a(n) = 2*n*a(n-1) + 1 with a(0) = 1.

Terms

a(0) =1a(1) =3a(2) =13a(3) =79a(4) =633a(5) =6331a(6) =75973a(7) =1063623a(8) =17017969a(9) =306323443a(10) =6126468861a(11) =134782314943