a(n) = Sum_{d|n} (-1)^(d-1)*d^3.

Terms

a(0) =1a(1) =-7a(2) =28a(3) =-71a(4) =126a(5) =-196a(6) =344a(7) =-583a(8) =757a(9) =-882a(10) =1332a(11) =-1988a(12) =2198a(13) =-2408a(14) =3528a(15) =-4679a(16) =4914a(17) =-5299a(18) =6860a(19) =-8946a(20) =9632a(21) =-9324a(22) =12168a(23) =-16324a(24) =15751a(25) =-15386a(26) =20440a(27) =-24424a(28) =24390a(29) =-24696