Expansion of g^3/(1 + x*g)^2, where g = 1+x*g^2 is the g.f. of A000108.

Terms

a(0) =1a(1) =1a(2) =4a(3) =11a(4) =35a(5) =113a(6) =376a(7) =1276a(8) =4402a(9) =15390a(10) =54408a(11) =194169a(12) =698567a(13) =2530937a(14) =9226160a(15) =33815432a(16) =124538318a(17) =460644494a(18) =1710476504a(19) =6373775030a(20) =23826843614a(21) =89331823706a(22) =335823046544