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A285021
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Denominator of binomial(2*n,n)/20^n.
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2
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1, 10, 200, 400, 16000, 800000, 16000000, 160000000, 2560000000, 25600000000, 2560000000000, 25600000000000, 1024000000000000, 409600000000000, 8192000000000000, 409600000000000000, 65536000000000000000, 655360000000000000000, 2621440000000000000000, 26214400000000000000000, 5242880000000000000000000, 52428800000000000000000000
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OFFSET
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0,2
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LINKS
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FORMULA
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A285020(n)/a(n) = (-1/5)^n*sqrt(Pi)/(Gamma(1/2 - n)*Gamma(1 + n)).
Sum_{k>=0} A285020(k)/a(k) = sqrt(5)/2.
Sum_{k>=0} (-1)^k*A285020(k)/a(k) = sqrt(5/6).
Sum_{k>=0} (-1)^(k+1)*A285020(k)/a(k) = -sqrt(5/6).
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MATHEMATICA
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Denominator[Table[(-1/5)^n*Sqrt[Pi]/(Gamma[1/2-n]*Gamma[1+n]), {n, 0, 25}]]
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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STATUS
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approved
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