a(n) = Sum_{0<d|n, n/d odd} d^7.

Terms

a(0) =1a(1) =128a(2) =2188a(3) =16384a(4) =78126a(5) =280064a(6) =823544a(7) =2097152a(8) =4785157a(9) =10000128a(10) =19487172a(11) =35848192a(12) =62748518a(13) =105413632a(14) =170939688a(15) =268435456a(16) =410338674a(17) =612500096a(18) =893871740a(19) =1280016384a(20) =1801914272a(21) =2494358016a(22) =3404825448