G.f.: Sum_{n>=0} x^n/(1-x)^(4*n) * Sum_{k=0..n} C(n,k)^2 * x^k.

A249792

G.f.: Sum_{n>=0} x^n/(1-x)^(4*n) * Sum_{k=0..n} C(n,k)^2 * x^k.

Terms

    a(0) =1a(1) =1a(2) =6a(3) =27a(4) =121a(5) =555a(6) =2586a(7) =12182a(8) =57867a(9) =276694a(10) =1330065a(11) =6421593a(12) =31117227a(13) =151254410a(14) =737182800a(15) =3601225529a(16) =17628257696a(17) =86446992591a(18) =424605995273

External references