a(n) = Sum_{d|n, d == 1 mod 4} d^2 - Sum_{d|n, d == 3 mod 4} d^2.

Terms

a(0) =1a(1) =1a(2) =-8a(3) =1a(4) =26a(5) =-8a(6) =-48a(7) =1a(8) =73a(9) =26a(10) =-120a(11) =-8a(12) =170a(13) =-48a(14) =-208a(15) =1a(16) =290a(17) =73a(18) =-360a(19) =26a(20) =384a(21) =-120a(22) =-528a(23) =-8a(24) =651a(25) =170a(26) =-656a(27) =-48a(28) =842a(29) =-208