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

Terms

a(0) =1a(1) =127a(2) =2188a(3) =16255a(4) =78126a(5) =277876a(6) =823544a(7) =2080639a(8) =4785157a(9) =9922002a(10) =19487172a(11) =35565940a(12) =62748518a(13) =104590088a(14) =170939688a(15) =266321791a(16) =410338674a(17) =607714939a(18) =893871740a(19) =1269938130a(20) =1801914272a(21) =2474870844a(22) =3404825448a(23) =4552438132a(24) =6103593751a(25) =7969061786a(26) =10465138360a(27) =13386707720a(28) =17249876310