This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A385309 #15 Jun 26 2025 07:41:27
%S A385309 1,1,4,31,328,4485,75520,1509347,34916224,917703145,27011107840,
%T A385309 880133628231,31451749424128,1223047891889837,51414400611438592,
%U A385309 2323391075748100555,112315439676217262080,5783449255108473820497,316034972288791445241856,18265740423344520141491951
%N A385309 Expansion of e.g.f. 1/(1 - 3 * x * cosh(x))^(1/3).
%F A385309 a(n) = Sum_{k=0..n} A007559(k) * A185951(n,k), where A185951(n,0) = 0^n.
%o A385309 (PARI) a185951(n, k) = binomial(n, k)/2^k*sum(j=0, k, (2*j-k)^(n-k)*binomial(k, j));
%o A385309 a007559(n) = prod(k=0, n-1, 3*k+1);
%o A385309 a(n) = sum(k=0, n, a007559(k)*a185951(n, k));
%Y A385309 Cf. A205571, A385308.
%Y A385309 Cf. A380017, A385305, A385307, A385311.
%Y A385309 Cf. A007559, A185951, A352649, A385282.
%K A385309 nonn
%O A385309 0,3
%A A385309 _Seiichi Manyama_, Jun 24 2025