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The Binary Totient Series

Erdős #249 By July 2026; revised 1 October 2026 Authorship, AI use and citation

Summary. The dyadic totient sections through level e≥1 have an explicit rational basis of size 2e+1. Truncating a scaled tail difference produces an integer whose residue certifies nonintegrality when its distances from both endpoints of the residue interval exceed an explicit error bound. The record develops the resulting finite denominator exclusions, equivalent residue criteria, and sufficient exponential-sum estimates. Rational comparison sequences identify the limitations of particular size, parity, rank, and finite-prefix arguments. The short paper supplies the all-base basis theorem; here each conditional result carries the arithmetic hypothesis still needed to apply it. Those hypotheses are not established in the form required to prove irrationality of S=∑ φ(n)2−n.

This paper covers a claim-bounded problem-specific reasoning surface for Erdős #249: selected checked premises, finite certificates, closed routes, surviving obligations, and their exact evidence bands.

It does not establish the validity of claims tagged Lean, which belongs to the cited kernel-checked source, or a solution to Erdős #249, which remains open.

In this paper

The actual tail difference on the LCM diagonal

For H=H2a, the actual difference Ωa=R2H−RH removes the auxiliary rational approximation from the LCM criterion. The equivalence below restricts attention to this sparse sequence of tails. Its required nonintegrality is still an arithmetic assertion to prove.

The exact equivalence.

S∉Q⟺∀a0, ∃a≥a0, Ωa∉Z.

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.irrational_totientSeries_iff_actualLcmOrbitNonintegralitySupply This is an unconditional equivalence, where Ωa:=2H(2H−1)S−(Φ2H−ΦH), H=H2a (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.actualLcmTailOrbit_eq_scaled_totientSeries_sub_prefix). The right-hand side is an equivalent reformulation of irrationality, not a weaker hypothesis already established by the finite examples. The following sufficient conditions are attempts to prove it.

An impossible complete divisibility pattern

Let a≥8, H=H2a and J,K,m∈N, with

m≤K,J+K+a+6<2⋅2a,B:=2H+J+K+2<2m.

It is impossible that

2r+1∣δ2a(J+K−m+r+1)for every 0≤r<m.

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.not_actualLcmTerminalDyadicStaircase_of_room Indeed, the last requirement would make δ2a(J+K) a multiple of 2m, whereas the short-window bounds give 0<δ2a(J+K)<B<2m. The positivity input is

δ2a(j)>0(a≥8, 0<j<2⋅2a),

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.lcmRayArithmeticLetter_pos_of_lt_two_mul, without a rationality hypothesis.

Omitting only the last divisibility requirement leaves the partial pattern in Proposition 6.86. It additionally requires δ2a(J+K)≤2m−B. The resulting necessary equality is penultimate:

δ2a(J+K−1)=2m−1,B<2m<2B.

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.puncturedDyadicStaircase_penultimate_eq_half The terminal difference is not pinned to 2m−1. Neither this necessary restriction nor the full-pattern impossibility supplies an unbounded family of successful partial patterns.

The remaining upper-endpoint residue
Ga(J,K,m):≡m≤K ∧ 2H+J+K+2<2m ∧ D(H,H+J,K)mod2m≤2m−(2H+J+K+2).

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.ActualLcmTopEdgeResidueGap No unbounded family satisfying this condition is known.

The positivity theorem gives

R2H+J−RH+J>0if a≥8 and J+a+6<2⋅2a.

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.actualLcmTailDiff_shift_pos For a≥8, the residue test at depth K uses the stronger bound J+K+a+6<2⋅2a. Under these hypotheses, an integral initial tail difference would give an integer terminal carry e=R2H+J+K−RH+J+K with 0<e<2H+J+K+2. The tail identity is

D(H,H+J,K)=2K(R2H+J−RH+J)−e.

Hence, when 2H+J+K+2<2K, it is the residue of D(H,H+J,K), not of e, that equals 2K−e (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.actualLcm_integral_forces_topEdgeResidue). More generally, the bounds m≤K and 2H+J+K+2<2m give

D(H,H+J,K)mod2m=2m−e>2m−(2H+J+K+2),

because 2m divides 2K and 0<e<2m. This contradicts Ga(J,K,m). Consequently, for a≥8 and J+K+a+6<2⋅2a,

Ga(J,K,m)⟹R2H+J−RH+J∉Z.

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.actualLcmTailDiff_notMem_int_of_topEdgeResidueGap The one-sided inequality excludes the upper-endpoint interval forced by integrality. Positivity alone does not establish that inequality.

The cofinal target built from it is

cofinal upper-endpoint condition:≡ ∀a0, ∃a,K,m,a0≤a ∧ 8≤a ∧ K+(a+6)<2⋅2a ∧ Ga(0,K,m).

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.PowerTwoActualLcmTopEdgeResidueGapSupply This condition is unproved; its implication is proved:

cofinal upper-endpoint condition⟹S∉Q.

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.irrational_totientSeries_of_topEdgeResidueGapSupply

Five sufficient conditions for that residue inequality

The next five quantified conditions each imply irrationality. Conditions (i)–(iv) reach the upper-endpoint test; (v) gives nonintegrality directly. Their proven relations are summarised in Proposition 6.65.

  1. For every a0, there are a≥max(a0,8) and m≥0 with H=H2a such that

    m+1+a+6<2⋅2a,2H+m+3<2m,2H+m+2≤(D(H,H,m)+δ2a(m+1))mod2m≤2m−(2H+m+3),

    where δ2a(j)=φ(2H+j)−φ(H+j). The size condition includes the larger depth m+1, so the conclusion remains valid whichever of the two adjacent depths gives the certificate. This condition is unproved (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.PowerTwoAdjacentSuffixMidbandSupply); its sufficiency is proved (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.powerTwoActualLcmTopEdgeResidueGapSupply_of_adjacentSuffixMidband, Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.irrational_totientSeries_of_adjacentSuffixMidbandSupply).

  2. For every a0, there is a≥max(a0,14) with the following property. Put H=H2a and choose q so that 2q+1 is the least odd integer not smaller than ⌊log2⁡H⌋+10. Define integers Wa,j recursively by

    Wa,0=0,Wa,j+1=4Wa,j+δ2a(2j+3)−2δ2a(2j+2)+δ2a(2j+4)2.

    The increments δ2a(s) are even, so the recurrence is integral. The required inequality is

    H+q+2≤Wa,qmod4q≤4q−(H+q+2).

    At depth m=2q+1, the residue in (i) equals 2(Wa,qmod4q). Dividing its two endpoint bounds by 2 and using integrality gives exactly the threshold H+q+2. This condition is unproved (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.PowerTwoOddGuardTopEdgeHalfWordBandSupply). The width is H+q+2 and the depth is the prescribed depth; both must be retained when comparing this with a fixed-fraction band. Its sufficiency is proved (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.powerTwoAdjacentSuffixMidbandSupply_of_oddGuardTopEdgeHalfWordBand).

  3. Use exactly the quantifiers and prescribed depth of (ii). Let r=Wa,qmod4q and define its centred representative by

    ua,q={r,2r≤4q,r−4q,2r>4q.

    Thus −4q/2<ua,q≤4q/2; when a midpoint occurs, the positive representative is used. The equivalent inequality is

    H+q+2≤|ua,q|.

    This condition is unproved (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.PowerTwoActualFinalTopEdgeMagnitudeSupply). At the prescribed depth the size bound 2(H+q+2)≤4q holds. For a residue in [0,4q), the band in (ii) is therefore exactly this absolute-value condition. The equivalence, including its quantifiers, is proved (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.topEdgeHalfWordBandSupply_iff_actualFinalCenteredMagnitudeSupply).

  4. Allow the odd depth to vary, but retain both size bounds. For every a0, require a≥max(a0,8) and q∈N with

    2q+2+a+6<2⋅2a,2(H+q+2)≤4q,H+q+2≤|ua,q|,H=H2a.

    This condition is unproved (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.PowerTwoFlexibleActualTopEdgeMagnitudeSupply). The first bound keeps the adjacent depth inside the short window; the second makes the required residue band nonempty. One implication passes through (i), and another gives the two-sided carry exclusion below (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.powerTwoAdjacentSuffixMidbandSupply_of_flexibleActualTopEdgeMagnitude, Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.irrational_totientSeries_of_flexibleActualTopEdgeMagnitudeSupply).

  5. Retain the full quantifiers and the two size bounds in (iv), but replace its absolute-value inequality by

    δ2a(2q+2)≤2ua,q.

    This compares the signed centred residue with the terminal totient difference. It is not an unrestricted assertion at an arbitrary q. This condition is unproved (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.PowerTwoFlexibleActualTerminalDominanceSupply); its sufficiency is proved (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.irrational_totientSeries_of_flexibleActualTerminalDominanceSupply).

A further sufficient terminal-carry condition

With H=H2a, the unproved quantified condition is

∀a0 ∃a≥max(a0,8) ∃q:2q+2+(a+6)<2⋅2a,2(H+q+2)≤4q,2ua,q≤δ2a(2q+2)−(2H+2q+3)orδ2a(2q+2)≤2ua,q.

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.PowerTwoFlexibleActualTerminalCarryCorridorEscapeSupply Either alternative gives nonintegrality at that scale, so the quantified condition implies irrationality (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.irrational_totientSeries_of_flexibleActualTerminalCarryCorridorEscapeSupply).

The proof assumes an integer z=Ωa and uses

2ua,q=δ2a(2q+2)−cH,H,z(2q+1).

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.two_mul_actualOddHalfCenteredLift_eq_terminal_sub_trueCarry The carry is then a positive tail difference, strictly smaller than 2H+2q+3. The negative endpoint representative is minus this carry (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.actualLcm_trueEndpointSurvivor_neg). The first alternative contradicts the upper bound; the second contradicts positivity, which is the terminal-dominance argument (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.actualLcmTailOrbit_notMem_int_of_actualTerminalDominance).

Both arguments are conditional contradictions, not evidence against either unproved estimate. No converse from nonintegrality to either finite inequality is asserted. In particular, the exact identity must not be described as making this sufficient condition necessary.

Certificates in short windows

For every t,j∈N, the arithmetic difference on the LCM progression is exactly

δt(j)=φ(2Ht+j)−φ(Ht+j).

No coprimality restriction on j is needed (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.lcmRayArithmeticLetter_eq_deltaTotient). Consequently the corresponding window numerator is

D(Ht,Ht,L)=∑j=1Lδt(j)2L−j,

and applying the same residue and error bounds gives precisely the test C(Ht,Ht,L) (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.lcmDiagonalArithmeticKill_iff_certifiedKill). Thus the quantified assertion

∀a0 ∃a≥a0 ∃L<2⋅2a,C(H2a,H2a,L)

implies irrationality (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.PowerTwoActualLcmShortArithmeticKillSupply, Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.actualLcmOrbitNonintegralitySupply_of_shortArithmeticKill); the assertion itself is unproved. It restricts the diagonal indices to powers of two and imposes the additional bound L<2⋅2a. Pointwise completeness allows an unspecified finite depth; it does not imply a witness within this short window.

The displayed certified examples have a=4, L=23 and a=6, L=93 (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.actualLcmTailOrbit_four_and_six_notMem_int); these are finite computations. The bounded statement of Theorem 9.22 uses the single witness (a,L)=(6,93) to cover all thresholds a0≤6. It makes no assertion for larger thresholds, or that these are the only successful exponents.

A sufficient approximation bound

Put H=H2a and define the finite rational and its error bound by

ρa,q=D(H,H,2q+1)+δ2a(2q+2)22q+1,εa,q=2H+2q+322q+1.

For every a,q∈N,

|Ωa−ρa,q|<εa,q.

Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.abs_actualLcmTailOrbit_sub_rawApprox_lt Let 2qa+1 be the least odd integer not smaller than ⌊log2⁡H⌋+10, as in condition (ii). The sufficient quantified separation condition is

∀a0 ∃a≥max(2,a0) ∀z∈Z,132+εa,qa≤|Ωa−z|.

This condition is unproved; its sufficiency is proved (Erdos249257.DiagonalFreshLossBridge.PowerTwoOddWindowAffine.irrational_totientSeries_of_actualLcmOrbitSeparationSupply). The triangle inequality then gives |ρa,qa−z|>1/32 for every integer z. The hypothesis concerns the real tail Ωa, not merely its computable approximant. The truncation estimate transfers the stated separation, but does not itself establish it. Also, the depth is prescribed by a; it is not a free parameter in this hypothesis.

About this paper

Authorship and AI use. Will Cook built and directed the research infrastructure and maintains the public release. He reviewed claims when he could. AI agents did most of the research and drafting. Cook did not independently verify every claim.

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