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

Author

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

Keywords

• sign

Programs

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 *)