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 A379660 #7 Dec 29 2024 08:49:06
%S A379660 1,4,63,1861,82097,4850511,360275791,32284172215,3391036374849,
%T A379660 408722465393947,55615320933323831,8433939560030789091,
%U A379660 1410592999486776429841,257966146919938099737511,51211682886276933924579999,10968423456294584033965364191,2521058533839507726700577317889
%N A379660 Expansion of e.g.f. (1/x) * Series_Reversion( x * (exp(-x) - 3*x) ).
%F A379660 a(n) = n! * Sum_{k=0..n} 3^(n-k) * (2*n-k+1)^(k-1) * binomial(2*n-k+1,n-k)/k!.
%o A379660 (PARI) a(n) = n!*sum(k=0, n, 3^(n-k)*(2*n-k+1)^(k-1)*binomial(2*n-k+1, n-k)/k!);
%Y A379660 Cf. A000272, A377890, A379659.
%K A379660 nonn
%O A379660 0,2
%A A379660 _Seiichi Manyama_, Dec 29 2024