E.g.f.: exp(2*arcsin(x)).

Terms

a(0) =1a(1) =2a(2) =4a(3) =10a(4) =32a(5) =130a(6) =640a(7) =3770a(8) =25600a(9) =199810a(10) =1740800a(11) =16983850a(12) =181043200a(13) =2122981250a(14) =26794393600a(15) =367275756250