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 A365975 #9 Sep 24 2023 09:16:16
%S A365975 1,1,2,6,30,180,1260,10800,104760,1130760,13776480,184044960,
%T A365975 2670220080,42222280320,718144004160,13061603808000,254036916144000,
%U A365975 5247117638294400,114652672773408000,2647321293055507200,64330669872690566400,1640738743703289331200
%N A365975 Expansion of e.g.f. 1 / ( 1 - Sum_{k>=0} x^(3*k+1) / (3*k+1) ).
%F A365975 a(0) = 1; a(n) = Sum_{k=0..floor((n-1)/3)} (3*k)! * binomial(n,3*k+1) * a(n-3*k-1).
%o A365975 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1-sum(k=0, N\3, x^(3*k+1)/(3*k+1)))))
%Y A365975 Cf. A296676, A365976, A365977.
%K A365975 nonn
%O A365975 0,3
%A A365975 _Seiichi Manyama_, Sep 23 2023