Expansion of g/(1 - x^4*g^4), where g = 1+x*g^2 is the g.f. of A000108.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =47a(6) =152a(7) =504a(8) =1706a(9) =5872a(10) =20490a(11) =72319a(12) =257723a(13) =926071a(14) =3351552a(15) =12205864a(16) =44698318a(17) =164492726a(18) =608009172a(19) =2256266234a(20) =8402790998a(21) =31395570766a(22) =117652696392a(23) =442095949780