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

Terms

a(0) =1a(1) =0a(2) =1a(3) =-2a(4) =5a(5) =-4a(6) =13a(7) =-27a(8) =89a(9) =-80a(10) =191a(11) =-450a(12) =2365a(13) =-1182a(14) =3221a(15) =-13034a(16) =40433a(17) =-22320a(18) =96373a(19) =-193761a(20) =772981a(21) =-728930a(22) =1599357a(23) =-3428425a(24) =21411337a(25) =-13595724a(26) =31407273a(27) =-110011850a(28) =377746853a(29) =-198079308