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A009126
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Expansion of e.g.f. cosh(log(1+tanh(x))).
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2
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1, 0, 1, -3, 4, 0, 16, -168, 64, 3840, 256, -177408, 1024, 11182080, 4096, -951886848, 16384, 104932638720, 65536, -14544442687488, 262144, 2475749026037760, 1048576, -507711943255523328, 4194304, 123460740095095603200, 16777216
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OFFSET
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0,4
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LINKS
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FORMULA
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E.g.f.: (1/Q(0)+Q(0))/2, where Q(k) = 1 - x/( 2*k+1 + x/Q(k+1) ); (continued fraction). - Sergei N. Gladkovskii, Dec 20 2013
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MATHEMATICA
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With[{nn=30}, CoefficientList[Series[Cosh[Log[1+Tanh[x]]], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, May 18 2014 *)
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PROG
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(PARI) x='x+O('x^30); Vec(serlaplace(cosh(log(1+tanh(x))))) \\ G. C. Greubel, Jul 28 2018
(Magma) m:=30; R<x>:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(Cosh(Log(1+Tanh(x))))); [Factorial(n-1)*b[n]: n in [1..m]]; // G. C. Greubel, Jul 28 2018
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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EXTENSIONS
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Previous Mathematica program replaced and definition clarified by Harvey P. Dale, May 18 2014
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STATUS
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approved
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