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 A368938 #10 Jan 10 2024 08:00:49
%S A368938 1,3,14,78,479,3129,21332,150057,1081118,7937589,59174752,446744610,
%T A368938 3408616155,26242751046,203615759472,1590550846398,12498584431503,
%U A368938 98731454253945,783581338236326,6245066800130298,49961547869830135,401076129627216180,3229808459696023980
%N A368938 Expansion of (1/x) * Series_Reversion( x * (1-x)^2 * (1-x+x^2) ).
%F A368938 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/2)} (-1)^k * binomial(n+k,k) * binomial(4*n-k+2,n-2*k).
%o A368938 (PARI) a(n) = sum(k=0, n\2, (-1)^k*binomial(n+k, k)*binomial(4*n-k+2, n-2*k))/(n+1);
%o A368938 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x*(1-x)^2*(1-x+x^2))/x)
%Y A368938 Cf. A129442, A368934.
%K A368938 nonn
%O A368938 0,2
%A A368938 _Seiichi Manyama_, Jan 10 2024