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 A326328 #11 Nov 25 2021 12:42:34 %S A326328 1,-3,33,-723,25953,-1376643,101031873,-9795436563,1212135593793, %T A326328 -186388033956483,34859622790687713,-7791941518975112403, %U A326328 2051293521728340489633,-628173356956461494680323,221398076445213367209575553,-88980467736394156270609236243,40450409313733718675802456121473 %N A326328 a(n) = (2*n)! [x^(2*n)] cosh(x)^(-3). %C A326328 Apparently all terms except the initial 1 have 3-valuation 1. - _F. Chapoton_, Nov 25 2021 %p A326328 egf := cosh(z)^(-3): ser := series(egf, z, 36): %p A326328 seq((2*n)!*coeff(ser, z, 2*n), n=0..16); %Y A326328 Row 3 of A326327. %K A326328 sign %O A326328 0,2 %A A326328 _Peter Luschny_, Jul 07 2019