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

A335309

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

Terms

    a(0) =1a(1) =3a(2) =22a(3) =245a(4) =3606a(5) =65527a(6) =1411404a(7) =35066313a(8) =985483270a(9) =30869546411

External references