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

A383379

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

Terms

    a(0) =1a(1) =1a(2) =4a(3) =21a(4) =176a(5) =1765a(6) =22464a(7) =331177a(8) =5692672a(9) =110286441a(10) =2394828800a(11) =57389046781

External references