Euler transform of 1, 3, 8, 23, ... (A050535).

Terms

a(0) =1a(1) =4a(2) =12a(3) =41a(4) =131a(5) =458a(6) =1574a(7) =5664a(8) =20766a(9) =78647a(10) =306438a(11) =1233636a(12) =5127670a(13) =22036940a(14) =97905965a(15) =449634928a(16) =2133165981a(17) =10445593354a(18) =52735714850a(19) =274162571129