A013338 Expansion of e.g.f.: sec(exp(x)-sec(x))=1+1/2!*x^2+9/4!*x^4-20/5!*x^5+177/6!*x^6...

1, 0, 1, 0, 9, -20, 177, -1260, 7105, -99144, 564049, -10278840, 77134761, -1412196188, 15082747617, -257693157540, 3771722331457, -62330454304272, 1150241027577697, -19671866661968880, 420212562193269513

Offset

0,5

Links

Table of n, a(n) for n=0..20.

Mathematica

With[{nn=20}, CoefficientList[Series[Sec[Exp[x]-Sec[x]], {x, 0, nn}], x] Range[ 0, nn]!] (* Harvey P. Dale, Feb 19 2020 *)

Crossrefs

Sequence in context: A230833 A321723 A282763 * A008847 A143243 A157812

Adjacent sequences: A013335 A013336 A013337 * A013339 A013340 A013341

Keyword

sign

Author

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

Extensions

Definition clarified by Harvey P. Dale, Feb 19 2020

Status

approved