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 A381787 #9 Mar 07 2025 10:48:48
%S A381787 1,2,5,22,112,623,3664,22405,141002,907228,5940663,39459873,265228359,
%T A381787 1800608563,12328843910,85040632504,590371016188,4121775003434,
%U A381787 28921911896836,203854515625194,1442669458817907,10247020573880520,73024240955785936,521973882076798493
%N A381787 G.f. A(x) satisfies A(x) = (1 + x) * C(x*A(x)), where C(x) is the g.f. of A000108.
%F A381787 a(n) = Sum_{k=0..n} binomial(3*k+1,k) * binomial(k+1,n-k)/(3*k+1).
%o A381787 (PARI) a(n) = sum(k=0, n, binomial(3*k+1, k)*binomial(k+1, n-k)/(3*k+1));
%Y A381787 Cf. A167422, A381785, A381786.
%Y A381787 Cf. A000108.
%K A381787 nonn
%O A381787 0,2
%A A381787 _Seiichi Manyama_, Mar 07 2025