A013448 sech(tan(x)-arctan(x))=1-160/6!*x^6+1792/8!*x^8-484224/10!*x^10...

1, 0, 0, -160, 1792, -484224, 54495232, -9441003520, 2598020579328, -756380393635840, 305071008569196544, -144297159065656885248, 81729693136918543335424, -55094722790449057575731200

Offset

0,4

Links

Table of n, a(n) for n=0..13.

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sech[Tan[x]-ArcTan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Feb 04 2016 *)

Crossrefs

Sequence in context: A013447 A013446 A013444 * A234650 A214354 A188306

Adjacent sequences: A013445 A013446 A013447 * A013449 A013450 A013451

Keyword

sign

Author

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

Status

approved