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Metadata 
bibkey: hanna2026a393857
authors: Paul D. Hanna
year: 2026
title: OEIS A393857, G.f. satisfies A(x - x*A(5*x)/5) = x
doi: null
url: https://oeis.org/A393857
claim: "G.f. A(x) satisfies A( x - x*A(5*x)/5 ) = x. Conjecture: a(n) == 1 (mod 6) for n >= 1."
strata_touched:
  - D5/S1/Recurrence/Invariants/ScaledReversionCongruence
license: citation-only
triage: anchor

OEIS A393857

Paul D. Hanna’s entry of March 11, 2026 defines the generating function by A( x - x*A(5*x)/5 ) = x and conjectures a(n) == 1 (mod 6) for n >= 1. The Lean module constructs the unique integer solution, proves the functional equation, and proves the congruence as the case q = 5 of a parametric theorem.

Verified locator

  • URL: https://oeis.org/A393857