A double product sequence based on a=2; f(n,a) = f(n-1,a) + a*f(n-2,a).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =3a(5) =1a(6) =1a(7) =15a(8) =15a(9) =1a(10) =1a(11) =55a(12) =275a(13) =55a(14) =1a(15) =1a(16) =231a(17) =4235a(18) =4235a(19) =231a(20) =1a(21) =1a(22) =903a(23) =69531a(24) =254947a(25) =69531a(26) =903a(27) =1a(28) =1a(29) =3655