a(n) = Sum_{k=1..n} (-1)^k*k^2*floor(n/k).

Terms

a(0) =-1a(1) =2a(2) =-8a(3) =11a(4) =-15a(5) =15a(6) =-35a(7) =48a(8) =-43a(9) =35a(10) =-87a(11) =103a(12) =-67a(13) =83a(14) =-177a(15) =162a(16) =-128a(17) =145a(18) =-217a(19) =277a(20) =-223a(21) =143a(22) =-387a(23) =443a(24) =-208a(25) =302a(26) =-518a(27) =432a(28) =-410a(29) =370