A012013 sech(sin(sin(x)))=1-1/2!*x^2+13/4!*x^4-373/6!*x^6+19545/8!*x^8...

1, -1, 13, -373, 19545, -1638569, 201324773, -34084249501, 7606559175089, -2164004651794513, 764464999664782013, -328322677491890500805, 168474698667902836871177, -101798128590699775451705081

Offset

0,3

Links

Table of n, a(n) for n=0..13.

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sech[Sin[Sin[x]]], {x, 0, nn}], x] Range[ 0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jul 27 2022 *)

Crossrefs

Sequence in context: A183472 A009040 A009085 * A082403 A171656 A320458

Adjacent sequences: A012010 A012011 A012012 * A012014 A012015 A012016

Keyword

sign

Author

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

Status

approved