A370720 G.f. A(x) satisfies A(x) = (1 + x*A(x)^(3/4) / (1+x))^4.
1, 4, 14, 56, 241, 1088, 5082, 24352, 119036, 591224, 2975150, 15136036, 77721311, 402276364, 2096572304, 10993229392, 57951531087, 306954017592, 1632807888084, 8719002979360, 46720890435026, 251149205370864, 1353974197346154, 7318852828505148
Offset: 0
Keywords
Programs
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PARI
a(n) = 4*sum(k=0, n, (-1)^(n-k)*binomial(n-1, n-k)*binomial(3*k+4, k)/(3*k+4));
Formula
a(n) = 4 * Sum_{k=0..n} (-1)^(n-k) * binomial(n-1,n-k) * binomial(3*k+4,k)/(3*k+4).