A013508 - OEIS

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A013508

cos(sec(x)-sech(x))=1-12/4!*x^4-5152/8!*x^8-7351872/12!*x^12...

1, -12, -5152, -7351872, 23844355328, 2971598628507648, 259172055916070309888, 31874732857037574011240448, 5625494806370311291378460131328, 1331819025115560536529968068424368128, 357000031318983624394235069073760267010048, 30988128279193785865476747562711031784709029888

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..11.

MATHEMATICA

With[{nn=50}, Take[CoefficientList[Series[Cos[Sec[x]-Sech[x]], {x, 0, nn}], x] Range[0, nn-2]!, {1, -1, 4}]] (* Harvey P. Dale, Nov 22 2014 *)

CROSSREFS

Sequence in context: A236067 A134821 A229669 * A230749 A003793 A171669

Adjacent sequences: A013505 A013506 A013507 * A013509 A013510 A013511

KEYWORD

sign

AUTHOR

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

EXTENSIONS

More terms from N. J. A. Sloane, Dec 17 2011

STATUS

approved