a(1) = 1; a(n+1) = -Sum_{d|n} a(n/d) * a(d).

Terms

a(0) =1a(1) =-1a(2) =2a(3) =-4a(4) =7a(5) =-14a(6) =32a(7) =-64a(8) =120a(9) =-244a(10) =502a(11) =-1004a(12) =1996a(13) =-3992a(14) =8048a(15) =-16124a(16) =32104a(17) =-64208a(18) =128712a(19) =-257424a(20) =514416a(21) =-1028960a(22) =2058924a(23) =-4117848a(24) =8233832a(25) =-16467713a(26) =32939418a(27) =-65879316a(28) =131750904a(29) =-263501808