a(n) = - Sum_{d|n} (-n/d)^d * binomial(d+n/d-2, d-1).

Terms

a(0) =1a(1) =1a(2) =4a(3) =-5a(4) =6a(5) =2a(6) =8a(7) =-121a(8) =172a(9) =44a(10) =12a(11) =-759a(12) =14a(13) =566a(14) =5536a(15) =-7665a(16) =18a(17) =-6877a(18) =20a(19) =2744a(20) =70862a(21) =21218a(22) =24a(23) =-570573a(24) =218776a(25) =104324a(26) =918568a(27) =942479a(28) =30a(29) =-3693495