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A013514 sec(sec(x)-sech(x)) = 1+12/4!*x^4+15232/8!*x^8+128432832/12!*x^12... 1
1, 12, 15232, 128432832, 3951670227712, 322851365262723072, 57788996387839852122112, 19922979338554898934445228032, 12060985210981195011358156168364032, 11959494452317925171268058230736426893312, 18398266125441128266076209600703368534212739072 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..10.

MAPLE

A013514 := proc(n)

        sec(sec(x)-sech(x)) ;

        coeftayl( %, x=0, 4*n) ;

        %*(4*n)! ;

end proc: # R. J. Mathar, Dec 16 2011

MATHEMATICA

With[{nn=40}, Take[CoefficientList[Series[Sec[Sec[x]-Sech[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 4}]] (* Harvey P. Dale, Dec 25 2017 *)

CROSSREFS

Sequence in context: A012735 A012674 A301533 * A340166 A125547 A159421

Adjacent sequences:  A013511 A013512 A013513 * A013515 A013516 A013517

KEYWORD

nonn

AUTHOR

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

EXTENSIONS

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

STATUS

approved

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Last modified March 3 03:03 EST 2021. Contains 341756 sequences. (Running on oeis4.)