a(0) = a(1) = 1; a(n) = [x^n] Product_{k=1..n-1} 1/(1 - x^a(k)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =6a(5) =8a(6) =11a(7) =14a(8) =19a(9) =24a(10) =30a(11) =37a(12) =47a(13) =57a(14) =70a(15) =84a(16) =102a(17) =121a(18) =144a(19) =170a(20) =202a(21) =235a(22) =275a(23) =319a(24) =372a(25) =429a(26) =495a(27) =567a(28) =652a(29) =742