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 A369503 #7 Jan 25 2024 07:49:40
%S A369503 1,4,24,168,1284,10384,87360,756704,6703168,60444928,552990592,
%T A369503 5120101760,47887472000,451759449600,4293634467840,41073654689280,
%U A369503 395170166443008,3821262491103232,37118973530660864,362035991963869184,3544080121528001536
%N A369503 Expansion of (1/x) * Series_Reversion( x / ((1+x)^2+x^2)^2 ).
%H A369503 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A369503 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/2)} binomial(2*n+2,k) * binomial(4*n-2*k+4,n-2*k).
%o A369503 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x/((1+x)^2+x^2)^2)/x)
%o A369503 (PARI) a(n) = sum(k=0, n\2, binomial(2*n+2, k)*binomial(4*n-2*k+4, n-2*k))/(n+1);
%Y A369503 Cf. A369502, A369504.
%K A369503 nonn
%O A369503 0,2
%A A369503 _Seiichi Manyama_, Jan 25 2024