a(n) = n! * Sum_{k=0..n} Stirling2(2*k,k) * Stirling2(2*n-2*k,n-k) / binomial(n,k).

A384470

a(n) = n! * Sum_{k=0..n} Stirling2(2*k,k) * Stirling2(2*n-2*k,n-k) / binomial(n,k).

Terms

    a(0) =1a(1) =2a(2) =29a(3) =1108a(4) =82924a(5) =10302768a(6) =1917699552a(7) =499332175200

External references