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

Terms

a(0) =1a(1) =0a(2) =2a(3) =5a(4) =15a(5) =40a(6) =136a(7) =429a(8) =1544a(9) =5686a(10) =22265a(11) =90714a(12) =386298a(13) =1705828a(14) =7806446a(15) =36899178a(16) =179843447a(17) =902128265a(18) =4650549252a(19) =24604524692a(20) =133442382601a(21) =741107102344