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 A366090 #7 Sep 28 2023 12:07:38
%S A366090 1,3,15,91,611,4370,32637,251550,1985895,15976676,130508070,
%T A366090 1079562159,9024791689,76124252326,647089873598,5537663661590,
%U A366090 47670889706375,412524981860848,3586502483999720,31311765471265548,274398528604427286
%N A366090 Expansion of (1/x) * Series_Reversion( x*(1-x)^4/(1-x-x^4) ).
%F A366090 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/4)} (-1)^k * binomial(n+1,k) * binomial(4*n-3*k+2,n-4*k).
%o A366090 (PARI) a(n) = sum(k=0, n\4, (-1)^k*binomial(n+1, k)*binomial(4*n-3*k+2, n-4*k))/(n+1);
%Y A366090 Cf. A366086, A366087, A366088, A366089.
%Y A366090 Cf. A366056.
%K A366090 nonn
%O A366090 0,2
%A A366090 _Seiichi Manyama_, Sep 28 2023