A013139 sec(tanh(x)+tan(x))=1+4/2!*x^2+80/4!*x^4+4288/6!*x^6+426240/8!*x^8...

1, 4, 80, 4288, 426240, 67920896, 15873495040, 5113806962688, 2172417489305600, 1176644688113041408, 791421023406538096640, 647183647775891247857664, 632330839348840678513704960

Offset

0,2

Links

Table of n, a(n) for n=0..12.

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sec[Tanh[x]+Tan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Feb 21 2023 *)

Crossrefs

Sequence in context: A012922 A013090 A012042 * A013007 A013008 A013180

Adjacent sequences: A013136 A013137 A013138 * A013140 A013141 A013142

Keyword

nonn

Author

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

Status

approved