E.g.f.: Product_{m>0} 1/(1 + x^m).

Terms

a(0) =1a(1) =-1a(2) =0a(3) =-6a(4) =24a(5) =-120a(6) =720a(7) =-5040a(8) =80640a(9) =-725760a(10) =7257600a(11) =-79833600a(12) =1437004800a(13) =-18681062400a(14) =261534873600