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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...
0
1, 0, 1, 0, 9, -20, 177, -1260, 7105, -99144, 564049, -10278840, 77134761, -1412196188, 15082747617, -257693157540, 3771722331457, -62330454304272, 1150241027577697, -19671866661968880, 420212562193269513
OFFSET
0,5
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
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
EXTENSIONS
Definition clarified by Harvey P. Dale, Feb 19 2020
STATUS
approved