G.f.: Sum_{n>=0} x^n * Product_{k=0..n-1} (1 + (2*k+1)*x).

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =13a(5) =40a(6) =127a(7) =443a(8) =1610a(9) =6207a(10) =24919a(11) =104440a(12) =453913a(13) =2042537a(14) =9488242a(15) =45403797a(16) =223433077a(17) =1128619968a(18) =5844484375a(19) =30981783123a(20) =167949231882a(21) =929951967519