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A364723
G.f. satisfies A(x) = 1 + x*A(x) / (1 - x*A(x)^4).
1
1, 1, 2, 8, 38, 196, 1073, 6120, 35968, 216304, 1324676, 8232981, 51796538, 329229344, 2111031444, 13638557196, 88695018723, 580153216512, 3814285704000, 25192499164320, 167075960048996, 1112162062296061, 7428213584196010, 49766086788057256
OFFSET
0,3
FORMULA
a(n) = (1/n) * Sum_{k=0..n-1} binomial(n,k) * binomial(n+3*k,n-1-k) for n > 0.
PROG
(PARI) a(n) = if(n==0, 1, sum(k=0, n-1, binomial(n, k)*binomial(n+3*k, n-1-k))/n);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Aug 05 2023
STATUS
approved