Expansion of Sum_{k>=1} (-1 + Product_{j>=1} 1/(1 - j*x^(k*j))).

Terms

a(0) =1a(1) =4a(2) =7a(3) =18a(4) =26a(5) =66a(6) =98a(7) =216a(8) =361a(9) =701a(10) =1171a(11) =2287a(12) =3763a(13) =6887a(14) =11707a(15) =20740a(16) =34637a(17) =60678a(18) =100581a(19) =172609a(20) =285924a(21) =481671a(22) =791317a(23) =1323831a(24) =2156856a(25) =3561119a(26) =5784021a(27) =9459559a(28) =15250217a(29) =24783964