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 A381782 #7 Mar 07 2025 10:47:29
%S A381782 1,2,9,52,342,2437,18331,143320,1153308,9489487,79470647,675149665,
%T A381782 5804359859,50402807459,441433999816,3894774605660,34585663823538,
%U A381782 308867647484634,2772256164853972,24994569816424301,226261997160303326,2055711320495566962
%N A381782 G.f. A(x) satisfies A(x) = (1 + x*A(x)^3) * C(x), where C(x) is the g.f. of A000108.
%F A381782 a(n) = Sum_{k=0..n} binomial(3*n-k+1,k) * binomial(3*n-3*k+1,n-k)/(3*n-k+1).
%o A381782 (PARI) a(n) = sum(k=0, n, binomial(3*n-k+1, k)*binomial(3*n-3*k+1, n-k)/(3*n-k+1));
%Y A381782 Cf. A212071, A381773, A381783.
%Y A381782 Cf. A000108.
%K A381782 nonn
%O A381782 0,2
%A A381782 _Seiichi Manyama_, Mar 07 2025