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A122252
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Binet's factorial series. Numerators of the coefficients of a convergent series for the logarithm of the Gamma function.
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2
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1, 1, 59, 29, 533, 1577, 280361, 69311, 36226519, 7178335, 64766889203, 32128227179, 459253205417, 325788932161, 2311165698322609, 287144996287039, 1215091897184850539, 402833263943353393, 476099430416027805187, 236881416523193720213, 650730651653461090091101
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OFFSET
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1,3
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LINKS
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FORMULA
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a(n) = numerator(c(n)), where c(n) are given by Binet's formulas:
log Gamma z = (z - 1/2) log z - z + log(2*Pi)/2 + Sum_{n >= 1} c(n)/(z+1)^(n), where z^(n) is the rising factorial.
c(n) = (1/n)*Integral_{x=0..1} x^(n)*(x - 1/2).
a(n) = numerator((1/2n)*Sum_{j=1..n} (-1)^(n-j)*Stirling1(n,j)*j/((j+1)*(j+2))). - Peter Luschny, Sep 22 2021
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EXAMPLE
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Rational sequence starts: 1/12, 1/12, 59/360, 29/60, 533/280, 1577/168, 280361/5040, ...
c(1) = Integral_{x=0..1} x*(x - 1/2) / 1 = Integral_{x=0..1} (x^2 - x/2) = (x^3/3 - x^2/4) | {x, 0, 1} = 1/12.
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MAPLE
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r := n -> add((-1)^(n-j)*Stirling1(n, j)*j/((j+1)*(j+2)), j=1..n)/(2*n):
a := n -> numer(r(n)); seq(a(n), n=1..21); # Peter Luschny, Sep 22 2021
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MATHEMATICA
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Rising[z_, n_Integer/; n>0] := z Rising[z + 1, n - 1]; Rising[z_, 0] := 1; c[n_Integer/; n>0] := Integrate[Rising[x, n] (x - 1/2), {x, 0, 1}] / n; Numerator@ Array[c, 19] (* updated by Robert G. Wilson v, Aug 15 2015 *)
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PROG
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(PARI) a(n) = numerator(sum(j=1, n, (-1)^(n-j)*stirling(n, j, 1)*j/((j+1)*(j+2)))/(2*n)); \\ Michel Marcus, Sep 22 2021
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CROSSREFS
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KEYWORD
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easy,frac,nonn
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AUTHOR
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Paul Drees (zemyla(AT)gmail.com), Aug 27 2006
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EXTENSIONS
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STATUS
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approved
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