a(n) = Sum_{d|n} (-1)^(n/d+1)*d^4.

Terms

a(0) =1a(1) =15a(2) =82a(3) =239a(4) =626a(5) =1230a(6) =2402a(7) =3823a(8) =6643a(9) =9390a(10) =14642a(11) =19598a(12) =28562a(13) =36030a(14) =51332a(15) =61167a(16) =83522a(17) =99645a(18) =130322a(19) =149614a(20) =196964a(21) =219630a(22) =279842a(23) =313486a(24) =391251a(25) =428430a(26) =538084a(27) =574078a(28) =707282a(29) =769980