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 A383262 #11 Apr 21 2025 09:55:09
%S A383262 0,0,1,12,123,1270,13776,158718,1944685,25294338,348340491,5064749074,
%T A383262 77528735868,1246096312188,20976610875949,368984700979440,
%U A383262 6767792258171547,129182459141936566,2561529454871582772,52676675861728386114,1121762199908797394977
%N A383262 Expansion of e.g.f. f(x)^2 * exp(f(x)) / 2, where f(x) = (exp(3*x) - 1)/3.
%F A383262 a(n) = Sum_{k=2..n} 3^(n-k) * binomial(k,2) * Stirling2(n,k).
%o A383262 (PARI) a(n) = sum(k=2, n, 3^(n-k)*binomial(k, 2)*stirling(n, k, 2));
%Y A383262 Cf. A003128, A383204.
%Y A383262 Cf. A286721.
%K A383262 nonn
%O A383262 0,4
%A A383262 _Seiichi Manyama_, Apr 21 2025