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 A379661 #7 Dec 29 2024 08:49:03
%S A379661 1,3,32,638,18992,757152,37946944,2294428880,162614380544,
%T A379661 13224995258624,1214230905887744,124244350629669888,
%U A379661 14021254268885487616,1730161184870597414912,231756218205467830255616,33492293939832097344370688,5194237715163522538324557824,860510764365813120075516739584
%N A379661 Expansion of e.g.f. (1/x) * Series_Reversion( x * (exp(-2*x) - x) ).
%F A379661 a(n) = n! * Sum_{k=0..n} 2^k * (2*n-k+1)^(k-1) * binomial(2*n-k+1,n-k)/k!.
%o A379661 (PARI) a(n) = n!*sum(k=0, n, 2^k*(2*n-k+1)^(k-1)*binomial(2*n-k+1, n-k)/k!);
%Y A379661 Cf. A377890, A379662.
%K A379661 nonn
%O A379661 0,2
%A A379661 _Seiichi Manyama_, Dec 29 2024