A376546 G.f. A(x) satisfies A(x) = 1 + x^4*(1+x)*A(x)^4.
1, 0, 0, 0, 1, 1, 0, 0, 4, 8, 4, 0, 22, 66, 66, 22, 140, 560, 840, 560, 1109, 4845, 9690, 9690, 11929, 43473, 106260, 141680, 160080, 419244, 1137304, 1883700, 2304432, 4496076, 12157236, 23614812, 32813500, 53821332, 132821856, 285795696, 451409380
Offset: 0
Keywords
Programs
-
PARI
a(n) = sum(k=0, n\4, binomial(k, n-4*k)*binomial(4*k, k)/(3*k+1));
Formula
a(n) = Sum_{k=0..floor(n/4)} binomial(k,n-4*k) * binomial(4*k,k)/(3*k+1).