A012804 tan(sec(x)*arctan(x))=x+3/3!*x^3+65/5!*x^5+2051/7!*x^7+154209/9!*x^9...

1, 3, 65, 2051, 154209, 14263139, 2239618017, 411001918627, 110281957937729, 33549045899804227, 13741520797366881025, 6244634409478025568963, 3628509505783902549611425, 2300839492251656581442561187

Offset

0,2

Comments

Note that a(131) is negative!. - Vaclav Kotesovec, Feb 07 2015

Links

Vaclav Kotesovec, Table of n, a(n) for n = 0..200

Mathematica

nn = 20; Table[(CoefficientList[Series[Tan[ArcTan[x]*Sec[x]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Feb 07 2015 *)

Crossrefs

Sequence in context: A112000 A216859 A346162 * A348084 A012837 A036778

Adjacent sequences: A012801 A012802 A012803 * A012805 A012806 A012807

Keyword

sign

Author

Patrick Demichel (patrick.demichel(AT)hp.com)

Status

approved