Product_{n>=1} 1 / (1 - a(n)*x^n) = 1 + Sum_{n>=1} sigma(n)*x^n, where sigma = A000203.

Terms

a(0) =1a(1) =2a(2) =1a(3) =-1a(4) =-3a(5) =-1a(6) =-1a(7) =-3a(8) =3a(9) =-17a(10) =-1a(11) =-6a(12) =3a(13) =-22a(14) =1a(15) =-28a(16) =1a(17) =-68a(18) =7a(19) =-262a(20) =-13a(21) =-199a(22) =27a(23) =-341a(24) =29a(25) =-647a(26) =3a(27) =-1431a(28) =-25a(29) =-476