login
A012839
sech(sec(x)*tanh(x))=1-1/2!*x^2+1/4!*x^4-97/6!*x^6+2945/8!*x^8...
0
1, -1, 1, -97, 2945, -148929, 15801729, -1624918817, 267458400513, -52723991194497, 12773658359030017, -3865567565691658721, 1370070916604727994497, -576252092267236760553793, 281775954919455982384816769, -158211465667174544221762575521
OFFSET
0,4
MATHEMATICA
With[{nn=40}, Take[CoefficientList[Series[Sech[Sec[x]Tanh[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jun 20 2017 *)
CROSSREFS
Sequence in context: A020538 A359639 A075665 * A017813 A017760 A069419
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
EXTENSIONS
More terms from Harvey P. Dale, Jun 20 2017
STATUS
approved