2007271089

Appears in sequences

• sec(arcsin(arctanh(x)))=1+1/2!*x^2+17/4!*x^4+769/6!*x^6+66849/8!*x^8...at n=6A012144
• Expansion of e.g.f. exp(arctanh(arctanh(x))).at n=12A012263