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Search: id:A134805
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| A134805 |
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Denominator of Sum_{i=1..n} 1/(i^2*binomial(2*i,i)). |
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+0
2
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| 1, 2, 24, 360, 2016, 16800, 237600, 151351200, 605404800, 30875644800, 53330659200, 6453009763200, 11416863427200, 1929449919196800, 1929449919196800, 93256746094512000, 680225677395264000, 196585220767231296000, 93119315100267456000, 1243794691794272409792000
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OFFSET
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0,2
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COMMENT
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For this sum times 2/3 see A130549/A130550 with offset 1.
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REFERENCES
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C. Elsner, On recurrence formulae for sums involving binomial coefficients, Fib. Q., 43 (No. 1, 2005), 31-45.
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FORMULA
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Sum_{i=1..infinity} 1/(i^2*binomial(2*i, i)) = Pi^2/18.
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EXAMPLE
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0, 1/2, 13/24, 197/360, 1105/2016, 9211/16800, 130277/237600, 82987349/151351200, ...
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CROSSREFS
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For numerators see A130549, n>=1.
Sequence in context: A013523 A081065 A043699 this_sequence A119702 A126804 A090114
Adjacent sequences: A134802 A134803 A134804 this_sequence A134806 A134807 A134808
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KEYWORD
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nonn,frac
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AUTHOR
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Wolfdieter Lang and N. J. A. Sloane (njas(AT)research.att.com), Oct 13 2008
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