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

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =9a(5) =14a(6) =19a(7) =24a(8) =45a(9) =75a(10) =105a(11) =135a(12) =229a(13) =359a(14) =503a(15) =647a(16) =1047a(17) =1591a(18) =2272a(19) =2972a(20) =4696a(21) =6996a(22) =9844a(23) =12894a(24) =20064a(25) =29538a(26) =41204a(27) =54407a(28) =84457a(29) =123723