G.f. satisfies A(x) = 1 + x + x^2*A(x)^5.

Terms

a(0) =1a(1) =1a(2) =1a(3) =5a(4) =15a(5) =55a(6) =220a(7) =876a(8) =3645a(9) =15485a(10) =66735a(11) =292155a(12) =1293456a(13) =5782320a(14) =26071435a(15) =118402495a(16) =541150155a(17) =2487204315a(18) =11488482130a(19) =53302256250a(20) =248293549685