a(n) = Sum_{d|n} (-1)^(d-1)*d^2.

Terms

a(0) =1a(1) =-3a(2) =10a(3) =-19a(4) =26a(5) =-30a(6) =50a(7) =-83a(8) =91a(9) =-78a(10) =122a(11) =-190a(12) =170a(13) =-150a(14) =260a(15) =-339a(16) =290a(17) =-273a(18) =362a(19) =-494a(20) =500a(21) =-366a(22) =530a(23) =-830a(24) =651a(25) =-510a(26) =820a(27) =-950a(28) =842a(29) =-780