G.f. A(x) satisfies A(x) = 1 + x/A(x) * (1 - A(x) + A(x)^4).

Terms

a(0) =1a(1) =1a(2) =2a(3) =8a(4) =32a(5) =145a(6) =681a(7) =3337a(8) =16773a(9) =86181a(10) =450268a(11) =2385544a(12) =12784861a(13) =69189509a(14) =377576512a(15) =2075423744a(16) =11480230037a(17) =63857579629a(18) =356962271136