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

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =12a(6) =35a(7) =133a(8) =497a(9) =2256a(10) =10123a(11) =53131a(12) =276210a(13) =1638039a(14) =9639943a(15) =63526677a(16) =416194299a(17) =3009639922a(18) =21672348693a(19) =170290649517