A012395 sech(tan(x)*tan(x))=1-12/4!*x^4-480/6!*x^6-15792/8!*x^8...

1, 0, -12, -480, -15792, 387840, 232592448, 44951262720, 4538494871808, -1173690989322240, -1020600368000166912, -406075179314308669440, -50036577406600515366912, 87776293107173235762462720

Offset

0,3

Links

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sech[Tan[x]^2], {x, 0, nn}], x] Range[ 0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Feb 27 2013 *)

Crossrefs

Sequence in context: A350154 A241226 A003749 * A012687 A012467 A009083

Adjacent sequences: A012392 A012393 A012394 * A012396 A012397 A012398

Keyword

sign

Author

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

Status

approved