G.f. satisfies: A(x) = 1 + x/A(-x*A(x)^2).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =11a(6) =31a(7) =98a(8) =317a(9) =1070a(10) =3685a(11) =12928a(12) =45924a(13) =164552a(14) =593398a(15) =2148288a(16) =7796846a(17) =28328601a(18) =102948125a(19) =373955584a(20) =1357252616a(21) =4921292287a(22) =17828236695a(23) =64546901169a(24) =233660589210a(25) =846258569786