Expansion of g.f.: x/((1-x^2)^5 - 1 + x).

Terms

a(0) =1a(1) =5a(2) =25a(3) =115a(4) =525a(5) =2385a(6) =10825a(7) =49120a(8) =222875a(9) =1011251a(10) =4588335a(11) =20818575a(12) =94459755a(13) =428590575a(14) =1944636420a(15) =8823364350a(16) =40034094615a(17) =181645987625a(18) =824179118751