G.f.: exp( Sum_{n>=1} x^n/n * Product_{k>=1} 1/(1 - x^(n*k)*(1 + x^k)^n) ).

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =11a(5) =26a(6) =56a(7) =125a(8) =269a(9) =578a(10) =1228a(11) =2600a(12) =5447a(13) =11366a(14) =23575a(15) =48664a(16) =99950a(17) =204383a(18) =416196a(19) =844299a(20) =1706368a(21) =3436555a(22) =6898255a(23) =13803732a(24) =27539833a(25) =54788703a(26) =108703105a(27) =215112006a(28) =424628345a(29) =836218453