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A143280
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Decimal expansion of m(2) = Sum_{n>=0} 1/n!!.
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17
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3, 0, 5, 9, 4, 0, 7, 4, 0, 5, 3, 4, 2, 5, 7, 6, 1, 4, 4, 5, 3, 9, 4, 7, 5, 4, 9, 9, 2, 3, 3, 2, 7, 8, 6, 1, 2, 9, 7, 7, 2, 5, 4, 7, 2, 6, 3, 3, 5, 3, 4, 0, 2, 0, 9, 2, 9, 9, 7, 1, 8, 7, 7, 9, 8, 0, 5, 4, 4, 2, 8, 1, 9, 6, 8, 4, 6, 1, 3, 5, 3, 5, 7, 4, 8, 1, 8, 5, 7, 4, 4, 8, 3, 4, 9, 7, 8, 2, 8, 3, 1, 5, 0, 1, 5
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OFFSET
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1,1
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COMMENTS
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Also decimal expansion of Sum_{n>=1} n!!/n!. - Michel Lagneau, Dec 24 2011
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LINKS
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FORMULA
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Equals sqrt(e) + sqrt((e*Pi)/2)*erf(1/sqrt(2)).
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EXAMPLE
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3.05940740534257614453947549923327861297725472633534020929971877980544281968...
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MATHEMATICA
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RealDigits[ Sqrt[E] + Sqrt[E*Pi/2]*Erf[1/Sqrt[2]], 10, 105][[1]] (* or *)
RealDigits[Total[1/Range[0, 200]!!], 10, 120][[1]] (* Harvey P. Dale, Apr 10 2022 *)
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PROG
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(PARI) default(realprecision, 100); exp(1/2)*(1 + sqrt(Pi/2)*(1-erfc(1/sqrt(2) ))) \\ G. C. Greubel, Mar 27 2019
(Magma) SetDefaultRealField(RealField(100)); R:= RealField(); Exp(1/2)*(1 + Sqrt(Pi(R)/2)*Erf(1/Sqrt(2) )) // G. C. Greubel, Mar 27 2019
(Sage) numerical_approx(exp(1/2)*(1 + sqrt(pi/2)*erf(1/sqrt(2))), digits=100) # G. C. Greubel, Mar 27 2019
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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