a(n) = (2*n)!*(2*n+1)! / (n! * (n+1)!)^2.
A000891
a(n) = (2*n)!*(2*n+1)! / (n! * (n+1)!)^2.
Terms
- a(0) =1a(1) =3a(2) =20a(3) =175a(4) =1764a(5) =19404a(6) =226512a(7) =2760615a(8) =34763300a(9) =449141836a(10) =5924217936a(11) =79483257308
External references
- oeis: A000891