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

Terms

a(0) =0a(1) =1a(2) =4a(3) =10a(4) =23a(5) =46a(6) =88a(7) =158a(8) =274a(9) =459a(10) =748a(11) =1190a(12) =1858a(13) =2846a(14) =4292a(15) =6384a(16) =9373a(17) =13602a(18) =19536a(19) =27782a(20) =39158a(21) =54740a(22) =75928a(23) =104562a(24) =143036a(25) =194423a(26) =262704a(27) =352988a(28) =471778a(29) =627382