Expansion of e.g.f. exp(arctanh(arctan(x))).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =9a(6) =49a(7) =57a(8) =-447a(9) =5169a(10) =78561a(11) =-93807a(12) =-5655231a(13) =31981689a(14) =1014069393a(15) =-3857766903a(16) =-187639949439