a(n) = (2*n)!*(2*n+1)! /((n+1)! *n!^3).

A000894

a(n) = (2*n)!*(2*n+1)! /((n+1)! *n!^3).

Terms

    a(0) =1a(1) =6a(2) =60a(3) =700a(4) =8820a(5) =116424a(6) =1585584a(7) =22084920a(8) =312869700a(9) =4491418360a(10) =65166397296a(11) =953799087696

External references