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A009131 Expansion of e.g.f. cosh(log(1+x))/cosh(x). 1
1, 0, 0, -3, 11, -30, 194, -1785, 13957, -113148, 1143284, -13131855, 156950639, -2005222362, 28119703702, -424785970245, 6792043718345, -115135087505400, 2072993596779944, -39432571052652315, 788564865102950035 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,4
LINKS
FORMULA
a(n) ~ n! * (-1)^n / (exp(1) + exp(-1)). - Vaclav Kotesovec, Jan 22 2015
MATHEMATICA
CoefficientList[Series[((1 + (1 + x)^2)*Sech[x])/(2*(1 + x)), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 22 2015 *)
PROG
(PARI) x='x+O('x^30); Vec(serlaplace(cosh(log(1+x))/cosh(x))) \\ G. C. Greubel, Jul 28 2018
(Magma) m:=30; R<x>:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(Cosh(Log(1+x))/Cosh(x))); [Factorial(n-1)*b[n]: n in [1..m]]; // G. C. Greubel, Jul 28 2018
CROSSREFS
Sequence in context: A330148 A085376 A196233 * A003554 A003523 A018781
KEYWORD
sign,easy
AUTHOR
EXTENSIONS
Extended with signs by Olivier Gérard, Mar 15 1997
STATUS
approved

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Last modified February 25 12:59 EST 2024. Contains 370328 sequences. (Running on oeis4.)