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 A379687 #8 Dec 30 2024 04:28:19
%S A379687 1,1,11,158,3597,107994,4082695,186003166,9930511577,608225910290,
%T A379687 42049314628251,3239451955702038,275220868466701861,
%U A379687 25565354021529630970,2577774089234276245391,280406846696018760511694,32732658189778781519050161,4081497882738710247779141922
%N A379687 Expansion of e.g.f. (1/x) * Series_Reversion( x * exp(x) * (1 - 2*x*exp(x)) ).
%F A379687 a(n) = (1/(n+1)) * Sum_{k=0..n} 2^(n-k) * (-k-1)^k * (2*n-k)!/(k! * (n-k)!).
%o A379687 (PARI) a(n) = sum(k=0, n, 2^(n-k)*(-k-1)^k*(2*n-k)!/(k!*(n-k)!))/(n+1);
%Y A379687 Cf. A379659, A379688.
%K A379687 nonn
%O A379687 0,3
%A A379687 _Seiichi Manyama_, Dec 29 2024