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

Terms

a(0) =1a(1) =2a(2) =-1a(3) =5a(4) =0a(5) =-3a(6) =-10a(7) =14a(8) =14a(9) =9a(10) =-2a(11) =-20a(12) =-33a(13) =-40a(14) =-25a(15) =71a(16) =54a(17) =54a(18) =35a(19) =5a(20) =26a(21) =15a(22) =-8a(23) =-80a(24) =-80a(25) =-93a(26) =-93a(27) =-135a(28) =-164a(29) =-149