G.f.: (1/(1 + x)) * Product_{k>=1} 1/(1 + x^prime(k)).

Terms

a(0) =1a(1) =-1a(2) =0a(3) =-1a(4) =2a(5) =-2a(6) =2a(7) =-3a(8) =4a(9) =-4a(10) =5a(11) =-7a(12) =8a(13) =-9a(14) =11a(15) =-13a(16) =15a(17) =-18a(18) =21a(19) =-24a(20) =28a(21) =-32a(22) =37a(23) =-43a(24) =49a(25) =-55a(26) =63a(27) =-72a(28) =81a(29) =-92