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 A376320 #12 Sep 20 2024 12:27:52
%S A376320 1,4,26,200,1691,15180,142038,1370076,13526645,136024876,1388394234,
%T A376320 14346699052,149790104030,1577765967600,16745718467070,
%U A376320 178912981116840,1922688816819276,20769064846817136,225384498769815750,2455985319885345820,26862562977746930145,294807644917408047060
%N A376320 G.f. satisfies A(x) = (1 + x*A(x)*(1 + x*A(x)))^4.
%H A376320 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A376320 If g.f. satisfies A(x) = (1 + x*A(x)*(1 + x*A(x))^s)^t, then a(n) = (1/(n+1)) * Sum_{k=0..n} binomial(t*(n+1),k) * binomial(s*k,n-k).
%F A376320 G.f.: (1/x) * Series_Reversion( x / (1+x+x^2)^4 ).
%F A376320 G.f.: B(x)^4, where B(x) is the g.f. of A365183.
%o A376320 (PARI) a(n, s=1, t=4) = sum(k=0, n, binomial(t*(n+1), k)*binomial(s*k, n-k))/(n+1);
%o A376320 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x/(1+x+x^2)^4)/x)
%Y A376320 Cf. A143927, A365128, A376328.
%Y A376320 Cf. A365183.
%K A376320 nonn
%O A376320 0,2
%A A376320 _Seiichi Manyama_, Sep 20 2024