a(n) = Sum_{k=1..n} (-1)^(k-1) * binomial(k+2,3) * floor(n/k).

Terms

a(0) =1a(1) =-2a(2) =9a(3) =-14a(4) =22a(5) =-27a(6) =58a(7) =-85a(8) =91a(9) =-97a(10) =190a(11) =-243a(12) =213a(13) =-266a(14) =460a(15) =-499a(16) =471a(17) =-553a(18) =778a(19) =-970a(20) =896a(21) =-845a(22) =1456a(23) =-1697a(24) =1264a(25) =-1560a(26) =2270a(27) =-2289a(28) =2207a(29) =-2307