a(n) = Sum_{d|n, n/d==1 mod 4} d^7 - Sum_{d|n, n/d==3 mod 4} d^7.

Terms

a(0) =1a(1) =128a(2) =2186a(3) =16384a(4) =78126a(5) =279808a(6) =823542a(7) =2097152a(8) =4780783a(9) =10000128a(10) =19487170a(11) =35815424a(12) =62748518a(13) =105413376a(14) =170783436a(15) =268435456a(16) =410338674a(17) =611940224a(18) =893871738a(19) =1280016384a(20) =1800262812a(21) =2494357760a(22) =3404825446a(23) =4584374272a(24) =6103593751