G.f.: Product_{i>=1} (1 - 2*(-x)^i)/(1 - (-x)^i)^2.

Terms

a(0) =0a(1) =-1a(2) =2a(3) =-4a(4) =4a(5) =-7a(6) =4a(7) =-5a(8) =0a(9) =5a(10) =-18a(11) =23a(12) =-46a(13) =65a(14) =-82a(15) =108a(16) =-132a(17) =152a(18) =-164a(19) =168a(20) =-144a(21) =132a(22) =-48a(23) =-39a(24) =212a(25) =-365a(26) =658a(27) =-947a(28) =1382a(29) =-1800