A013515 sech(sec(x)-sech(x))=1-12/4!*x^4+1568/8!*x^8+6840768/12!*x^12...

1, -12, 1568, 6840768, -41485549312, -616649036623872, 51689032519042469888, 309411873154808535072768

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: A366832 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