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

Terms

a(0) =1a(1) =2a(2) =5a(3) =14a(4) =40a(5) =121a(6) =383a(7) =1255a(8) =4298a(9) =15340a(10) =57061a(11) =221205a(12) =893281a(13) =3752361a(14) =16375447a(15) =74113910a(16) =347258809a(17) =1681355627a(18) =8397528329a(19) =43191571794a(20) =228416030275