Plectis
Erdős problem #249

The binary totient series

Is the binary Lambert series sum phi(n)/2^n irrational?

Open 3 Lean modules 3 main results Source directory

What is checked in Lean

  • Conditionally: a cofinal strict 9/10 gap for the exact natural prime-tail orbit supplies the existing finite pivot-point escape and hence the reviewed irrationality endpoint.
  • The local s=1 and s=2 squared Möbius Euler-factor identities and the first two prime-power divisor-sum differences.
  • That the two-by-two checkerboard kills separable backgrounds and is unique up to scale under the four row and column cancellations.
  • An abstract four-point divisor-layer identity, stated from its four explicit factorisation hypotheses.
  • An affine completion no-go: every residue class modulo an even modulus has a digit that recentres one carry step.
  • Exact producer and consumer interfaces for prime-ray layer supply, bounded-degree order witnesses, and finite-prime-support escape.

Main results

Statements and boundaries are copied from the corpus record. Registry status: not_registered; the claim registry does not carry these declarations and kernel checking them does not promote them into reviewed public claims

locally proved result; novelty unassessed family: totient_kernel_rank

For every e >= 1, the complete dyadic totient kernel through level e has rational span dimension 2^e + 1.

This does not prove irrationality of the totient series.

Lean formalisation of an existing consequence of Coons family: totient_kernel_rank

The rational span of the full dyadic totient kernel is not finite-dimensional.

The declaration is kernel-checked locally, but full-kernel infinite-dimensionality is not an independent contribution of this release; no rationality-to-finite-rank bridge is proved.

locally proved result; novelty unassessed family: totient_kernel_basis

The full dyadic totient kernel span admits the explicit odd-core-indexed basis.

The basis theorem does not connect rationality to finite kernel rank.

What is not checked

  • The strict prime-tail orbit gap, which is the unproved producer consumed by the conditional endpoint.
  • The packet's sharp parabolic Stern-Brocot cusp theorem and its passage from a geometric x-parameter to the arithmetic totient series.
  • Eventual Hankel nonvanishing for the Möbius-Mersenne power ladder, or its denominator obstruction.
  • The natural-boundary and quasimodular-transcendence steps of the infinite Euler-sieve tower.
  • Polynomial resultant realisability, exact-order finite-field supply, Frobenius freezing, or the Archimedean growth needed by the prime-ray strategy.
  • Unconditional irrationality of the binary totient series.

Open obligations

Prove any one of these and the corresponding reduction above becomes unconditional.

  • strict_prime_tail_orbit_gap Prove the cofinal strict 9/10 real-part gap for the exact natural prime-tail orbit, or replace it with another producer for the reviewed pivot-escape endpoint.
  • hankel_denominator_fan_in Prove eventual nonvanishing or a usable denominator obstruction for the Möbius-Mersenne power ladder and connect it to the target value.
  • euler_sieve_limit_theorem Control the infinite Euler-sieve limit strongly enough that finite-stage quasimodularity yields a valid arithmetic obstruction.
  • prime_ray_resultant_supply Realise the layer system by cyclic resultants and prove prime-support escape with the growth estimates needed to contradict a rational carry orbit.
  • stern_brocot_arithmetic_bridge Prove the sharp cusp asymptotic and then supply a non-formal bridge from the geometric parameter regime to the exact totient value.

Lean modules

Comparator review

The Comparator replays selected exact interfaces against a pinned toolchain. It never widens what Lean proved.

Replayed by the Comparator

Statement and type parity replayed against the pinned toolchain.

  • An explicit odd-core basis and relation normal form for the full dyadic totient kernel.

    The basis theorem does not connect rationality of the series to finite kernel rank.

    totient_kernel_basis · targeted

  • An independent constructive proof of exact finite-level dyadic rank 2^e+1, together with a kernel-checked full-kernel infinite-dimensionality corollary already implied by Coons's non-2-regularity theorem.

    Only the finite-level rank is presented as an additional result; full-kernel infinite-dimensionality is prior-art context, and no rationality-to-finite-rank bridge is proved.

    totient_kernel_rank · targeted

Represented indirectly

Covered through a neighbouring selected interface, not replayed one-to-one.

  • The totient series is rewritten as a Lambert series with explicit nonnegative, unbounded prime-power coefficients.

    The coefficient identities do not prove irrationality.

    totient_lambert_coefficients · represented_by_basis_and_rank_targets

Outside the Comparator selection

Stated in the corpus; not part of the replayed interface set.

  • For every base k at least 2, Lean checks the arithmetic reduction, exact nonmultiple-residue coordinates, unconditional canonical spanning, and exact rank k^e+1 conditional on canonical-family linear independence.

    Lean does not prove all-base affine-section independence or formalise Martin's theorem. The unconditional basis and rank conclusions in the paper use that external input.

    totient_kernel_all_base_index · not_selected_external_independence_boundary

  • A Farey denominator exclusion through 7.96e34, sharp for its selected window, and diagonal certificates through t=82.

    The selected finite window and certificate ceiling do not imply an unbounded producer.

    totient_finite_denominator_exclusion · not_selected_finite_family_has_separate_receipt

  • Rationality forces a tempered integral tail orbit with unbounded finite-level carry rank.

    This is a necessary consequence, not a contradiction.

    totient_carry_rank · not_selected_deep_orbit_vocabulary

  • Eventually periodic nonnegative rational weights give an irrational Lambert series.

    The totient-derived weights are not eventually periodic.

    eventually_periodic_lambert · not_selected_prior_result

  • Pointwise, cofinal, lcm-diagonal, and separated-window certificate supplies are exact or sufficient reformulations.

    Equivalent producer statements are as hard as the unresolved target.

    totient_certificate_equivalences · not_selected_deep_certificate_vocabulary

Palomar

One review unit is prepared for the Palomar lane: cmp:249:finrank_totient_kernel, status prepared_without_public_outcome. Preparation is not a submission, a review, or any recorded outcome. Route description

The paper

Problem note 19 pp

A Basis for the 2-Kernel of Euler's Totient

The dyadic sections of Euler's totient have an explicit rational basis: the true truncation has dimension 1 at level 0 and exactly 2^e + 1 for e at least 1, so the full span is infinite-dimensional. A 240-bit Farey window excludes every reduced denominator through 79,639,646,646,701,375,323,355,774,875,831,053, and exact diagonal certificates exist for every t through 82. No t = 83 certificate, cofinal supply, or matching rank upper bound is proved; Erdős #249 remains open.