a(n) = Sum_{k=0..n} C(n,k)*C(n+k,k)^3.

A218693

a(n) = Sum_{k=0..n} C(n,k)*C(n+k,k)^3.

Terms

    a(0) =1a(1) =9a(2) =271a(3) =11193a(4) =535251a(5) =27854739a(6) =1531656211a(7) =87547358649

External references