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A013515 sech(sec(x)-sech(x))=1-12/4!*x^4+1568/8!*x^8+6840768/12!*x^12... 1
1, -12, 1568, 6840768, -41485549312, -616649036623872, 51689032519042469888, 309411873154808535072768 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..7.

MAPLE

A013515 := proc(n)

        sech(sec(x)-sech(x)) ;

        coeftayl( %, x=0, 4*n) ;

        %*(4*n)! ;

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

CROSSREFS

Sequence in context: A299694 A160237 A013474 * A159383 A015011 A271435

Adjacent sequences:  A013512 A013513 A013514 * A013516 A013517 A013518

KEYWORD

sign

AUTHOR

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

STATUS

approved

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Last modified December 4 02:40 EST 2021. Contains 349469 sequences. (Running on oeis4.)