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 A379689 #9 Dec 30 2024 04:28:08
%S A379689 1,0,5,26,557,9504,254737,7405712,264468185,10599167744,484155176381,
%T A379689 24530813822976,1373346539948869,83980088153710592,
%U A379689 5576376312266516681,399370804845913339904,30695207044654060184753,2519882221014204064727040,220076205166821624927515893
%N A379689 Expansion of e.g.f. (1/x) * Series_Reversion( x * exp(x) * (1 - x*exp(2*x)) ).
%F A379689 a(n) = (1/(n+1)) * Sum_{k=0..n} (n-2*k-1)^k * (2*n-k)!/(k! * (n-k)!).
%o A379689 (PARI) a(n) = sum(k=0, n, (n-2*k-1)^k * (2*n-k)!/(k!*(n-k)!))/(n+1);
%Y A379689 Cf. A379661, A379690, A379691.
%K A379689 nonn
%O A379689 0,3
%A A379689 _Seiichi Manyama_, Dec 29 2024