a(n) = Sum_{d|n} (-1)^(d-1)*d^7.

Terms

a(0) =1a(1) =-127a(2) =2188a(3) =-16511a(4) =78126a(5) =-277876a(6) =823544a(7) =-2113663a(8) =4785157a(9) =-9922002a(10) =19487172a(11) =-36126068a(12) =62748518a(13) =-104590088a(14) =170939688a(15) =-270549119a(16) =410338674a(17) =-607714939a(18) =893871740a(19) =-1289938386a(20) =1801914272a(21) =-2474870844a(22) =3404825448a(23) =-4624694644a(24) =6103593751a(25) =-7969061786a(26) =10465138360a(27) =-13597534984a(28) =17249876310