a(0) = 1; a(n+1) = a(n)*2n + 2n + 1.

Terms

a(0) =1a(1) =1a(2) =5a(3) =25a(4) =157a(5) =1265a(6) =12661a(7) =151945a(8) =2127245a(9) =34035937a(10) =612646885a(11) =12252937721a(12) =269564629885