a(n) = Stirling2(2*n, n)*(2*n)!/(n+1)!.

A390727

a(n) = Stirling2(2*n, n)*(2*n)!/(n+1)!.

Terms

    a(0) =1a(1) =1a(2) =28a(3) =2700a(4) =571536a(5) =214326000a(6) =125799886080

External references