a(n) = Sum_{k=0..n} binomial(2*n+k-1,k) * binomial(2*n+k,n-k).

A379022

a(n) = Sum_{k=0..n} binomial(2*n+k-1,k) * binomial(2*n+k,n-k).

Terms

    a(0) =1a(1) =4a(2) =36a(3) =370a(4) =4012a(5) =44824a(6) =510498a(7) =5892310a(8) =68684540a(9) =806715964a(10) =9532070396a(11) =113179713046

External references