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

Terms

a(0) =1a(1) =-4a(2) =-13a(3) =-9a(4) =-34a(5) =11a(6) =-38a(7) =-38a(8) =-38a(9) =87a(10) =-34a(11) =-70a(12) =-239a(13) =6a(14) =231a(15) =231a(16) =-58a(17) =-58a(18) =-419a(19) =-519a(20) =-78a(21) =527a(22) =-2a(23) =-2a(24) =-2a(25) =843a(26) =843a(27) =647a(28) =-194a(29) =-1319