G.f.: Product_{m>0} (1-x^m+2!*x^(2*m)).

Terms

a(0) =1a(1) =-1a(2) =1a(3) =0a(4) =0a(5) =-3a(6) =4a(7) =-3a(8) =4a(9) =-2a(10) =0a(11) =-6a(12) =9a(13) =-10a(14) =10a(15) =-5a(16) =10a(17) =-16a(18) =20a(19) =-28a(20) =22a(21) =-18a(22) =19a(23) =-32a(24) =54a(25) =-50a(26) =45a(27) =-38a(28) =44a(29) =-78