A013503 E.g.f. exp(sec(x)-sech(x)) (even powers only).

1, 2, 12, 242, 8512, 438722, 34406592, 3496736882, 471749623552, 79119810366722, 16325059994068992, 4053422315328489842, 1187794482738667098112, 407438035244753039317442, 160833904474220565517811712, 72690404080321962122585230322

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Example

exp(sec(x)-sech(x)) = 1+2/2!*x^2+12/4!*x^4+242/6!*x^6+8512/8!*x^8...

Mathematica

With[{nn=40}, Take[CoefficientList[Series[Exp[Sec[x]-Sech[x]], {x, 0, nn}], x]Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Dec 23 2012 *)

Crossrefs

Sequence in context: A111403 A325501 A007986 * A231074 A132481 A369680

Adjacent sequences: A013500 A013501 A013502 * A013504 A013505 A013506

Keyword

nonn

Author

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

Extensions

Confirmed by N. J. A. Sloane, Dec 17 2011

More terms from Harvey P. Dale, Dec 23 2012

Status

approved