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A009125
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Expansion of e.g.f. cosh(log(1+tan(x))).
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2
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1, 0, 1, -3, 20, -120, 976, -8568, 88640, -1011840, 12933376, -180964608, 2767631360, -45799004160, 816582578176, -15594628021248, 317710534983680, -6876762625966080, 157606194409701376, -3812723805066559488
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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.: cosh(log(1+tan(x))).
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MATHEMATICA
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CoefficientList[Series[(1 + (1 + Tan[x])^2)/(2*(1 + Tan[x])), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 22 2015 *)
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PROG
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(PARI) x='x+O('x^30); Vec(serlaplace(cosh(log(1+tan(x))))) \\ G. C. Greubel, Jul 28 2018
(Magma) m:=30; R<x>:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(Cosh(Log(1+Tan(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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STATUS
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approved
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