Column 1 of triangle A109152.

Terms

a(0) =1a(1) =2a(2) =4a(3) =14a(4) =56a(5) =262a(6) =1348a(7) =7574a(8) =45616a(9) =292442a(10) =1978788a(11) =14060654a(12) =104403304a(13) =807162070a(14) =6476169012a(15) =53781863598a(16) =461194543136