G.f.: exp( Sum_{n>=1} (x^n/n) * Sum_{d|n} d*sigma(n/d,d) ).

Terms

a(0) =1a(1) =1a(2) =3a(3) =5a(4) =12a(5) =18a(6) =42a(7) =62a(8) =131a(9) =206a(10) =398a(11) =610a(12) =1203a(13) =1810a(14) =3358a(15) =5260a(16) =9471a(17) =14518a(18) =26182a(19) =39906a(20) =70320a(21) =108849a(22) =187251a(23) =287525a(24) =497288a(25) =758860a(26) =1286936a(27) =1986352a(28) =3330677a(29) =5102712