A366594 G.f. A(x) satisfies A(x) = 1 + x^3*(1+x)^3*A(x)^4.
1, 0, 0, 1, 3, 3, 5, 24, 60, 102, 258, 816, 1992, 4452, 12012, 33617, 84627, 212823, 577361, 1561077, 4063059, 10715009, 29052015, 78235107, 208358693, 560561391, 1522609569, 4120277283, 11129752269, 30240233739, 82441619605, 224488878600, 611770878012
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n\3, binomial(3*k, n-3*k)*binomial(4*k, k)/(3*k+1));
Formula
a(n) = Sum_{k=0..floor(n/3)} binomial(3*k,n-3*k) * binomial(4*k,k)/(3*k+1).