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 A371431 #10 Mar 23 2024 10:59:33
%S A371431 1,2,7,29,131,623,3064,15423,78936,408958,2137993,11252163,59508232,
%T A371431 315786764,1679410076,8941421014,47613443433,253359512287,
%U A371431 1346009853489,7133000408765,37669665812955,198034693198875,1035095172883710,5371011415598595,27615259784888724
%N A371431 Expansion of (1/x) * Series_Reversion( x * ((1-x)^2 + x^3) ).
%H A371431 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A371431 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} (-1)^k * binomial(n+k,k) * binomial(3*n-k+1,n-3*k).
%o A371431 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x*((1-x)^2+x^3))/x)
%o A371431 (PARI) a(n) = sum(k=0, n\3, (-1)^k*binomial(n+k, k)*binomial(3*n-k+1, n-3*k))/(n+1);
%Y A371431 Cf. A369214.
%K A371431 nonn
%O A371431 0,2
%A A371431 _Seiichi Manyama_, Mar 23 2024