G.f.: Sum_{n>=0} x^n / (1-x)^sigma(n).

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =12a(5) =29a(6) =71a(7) =175a(8) =438a(9) =1125a(10) =2961a(11) =7887a(12) =20949a(13) =54892a(14) =141198a(15) =357068a(16) =895592a(17) =2267345a(18) =5937586a(19) =16445988a(20) =48475348a(21) =149753749a(22) =472130021a(23) =1482046059a(24) =4556113875a(25) =13598311459a(26) =39278316217a(27) =109829580639a(28) =298021031162a(29) =787853185200