Product_{n>=1} (1 + x^n)^a(n) = 1 + Sum_{n>=1} phi(n) * x^n, where phi = A000010.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =-2a(6) =4a(7) =-3a(8) =4a(9) =-7a(10) =14a(11) =-21a(12) =30a(13) =-38a(14) =50a(15) =-79a(16) =128a(17) =-190a(18) =286a(19) =-419a(20) =598a(21) =-895a(22) =1386a(23) =-2121a(24) =3178a(25) =-4733a(26) =7122a(27) =-10796a(28) =16414a(29) =-25011