A379246 G.f. A(x) satisfies A(x) = ( (1 + x*A(x)^3)/(1 - x*A(x)) )^3.
1, 6, 90, 1838, 43362, 1111878, 30101786, 846703950, 24501770370, 724733787206, 21813611057562, 665947742487342, 20571682188676450, 641823879285627654, 20195381326042866138, 640146274715559742670, 20421757641058980395010, 655181707585675667750790, 21125606434257067959841242
Offset: 0
Keywords
Programs
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PARI
a(n) = sum(k=0, n, binomial(3*n+6*k+3, k)*binomial(4*n+5*k+2, n-k)/(n+2*k+1));
Formula
G.f.: B(x)^3 where B(x) is the g.f. of A379247.
a(n) = Sum_{k=0..n} binomial(3*n+6*k+3,k) * binomial(4*n+5*k+2,n-k)/(n+2*k+1).