589807203777domain: NAppears in sequencessec(arcsin(arctanh(x)))=1+1/2!*x^2+17/4!*x^4+769/6!*x^6+66849/8!*x^8...at n=7A012144Expansion of e.g.f. exp(arctanh(arctanh(x))).at n=14A012263