E.g.f.: exp(-Sum_{n>=1} sigma(n) * x^n).

Terms

a(0) =1a(1) =-1a(2) =-5a(3) =-7a(4) =1a(5) =839a(6) =4171a(7) =54305a(8) =102817a(9) =-4303441a(10) =-74521349a(11) =-1595325271a(12) =-20768141855a(13) =-222701825737