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

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =21a(5) =65a(6) =215a(7) =735a(8) =2585a(9) =9281a(10) =33883a(11) =125383a(12) =469229a(13) =1772801a(14) =6752623a(15) =25902975a(16) =99978865a(17) =388001025a(18) =1513077235a(19) =5926139207a(20) =23301146501a(21) =91942524481a(22) =363957103303