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

Terms

a(0) =0a(1) =0a(2) =2a(3) =-1a(4) =5a(5) =-3a(6) =9a(7) =-6a(8) =14a(9) =-10a(10) =20a(11) =-15a(12) =27a(13) =-21a(14) =35a(15) =-28a(16) =44a(17) =-36a(18) =54a(19) =-45a(20) =65a(21) =-55a(22) =77a(23) =-66a(24) =90a(25) =-78a(26) =104a(27) =-91a(28) =119a(29) =-105