G.f. A(x) satisfies A(x) = 1 + Sum_{n>=1} A(x)^n * x^n/(1 - x^(2*n)).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =16a(5) =49a(6) =156a(7) =512a(8) =1728a(9) =5959a(10) =20886a(11) =74204a(12) =266624a(13) =967141a(14) =3536814a(15) =13025478a(16) =48266972a(17) =179831935a(18) =673258626a(19) =2531481990a(20) =9555606112a(21) =36196916933a(22) =137554950152a(23) =524265889839