A366700 G.f. satisfies A(x) = (1 + x)^4 + x*A(x)^4.
1, 5, 26, 258, 3093, 40333, 558368, 8051416, 119614784, 1818190754, 28142073936, 442026009500, 7027713442496, 112879991541322, 1828959159551328, 29857735697705720, 490633308020085056, 8108894353260093213, 134705809490320133544
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n, binomial(4*(3*k+1), n-k)*binomial(4*k, k)/(3*k+1));
Formula
a(n) = Sum_{k=0..n} binomial(4*(3*k+1),n-k) * binomial(4*k,k)/(3*k+1).