Expansion of 1/(1-x^2*c(x)), c(x) the g.f. of A000108.

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =3a(5) =7a(6) =20a(7) =59a(8) =184a(9) =593a(10) =1964a(11) =6642a(12) =22845a(13) =79667a(14) =281037a(15) =1001092a(16) =3595865a(17) =13009673a(18) =47366251a(19) =173415176a(20) =638044203a(21) =2357941142a(22) =8748646386a(23) =32576869203a(24) =121701491701a(25) =456012458965