A012240 -log(cos(tan(x)))=1/2!*x^2+10/4!*x^4+232/6!*x^6+10064/8!*x^8...

1, 10, 232, 10064, 720384, 78009600, 11977120768, 2480763381760, 666957211828224, 225809770695098368, 93981332166180077568, 47151835657444566499328, 28061010401657661222289408

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..100

Formula

a(n) ~ 2*(2*n+1)! / arctan(Pi/2)^(2*n+2). - Vaclav Kotesovec, Jun 26 2014

Mathematica

With[{nn=30}, Take[CoefficientList[Series[-Log[Cos[Tan[x]]], {x, 0, nn}], x] Range[0, nn]!, {3, -1, 2}]] (* Harvey P. Dale, Jun 25 2014 *)

Crossrefs

Bisection of A009329 and A009387.

Sequence in context: A239773 A087434 A297648 * A295410 A188679 A167867

Adjacent sequences: A012237 A012238 A012239 * A012241 A012242 A012243

Keyword

nonn

Author

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

Extensions

Edited by D. S. McNeil, Dec 17 2011

Status

approved