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A056617
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Denominator of binomial(2*n,n) / (2*n+1).
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3
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1, 3, 5, 7, 9, 11, 13, 5, 17, 19, 21, 23, 25, 27, 29, 31, 11, 7, 37, 13, 41, 43, 3, 47, 49, 17, 53, 55, 57, 59, 61, 9, 65, 67, 23, 71, 73, 75, 11, 79, 81, 83, 17, 29, 89, 13, 31, 19, 97, 11, 101, 103, 35, 107, 109, 37, 113, 115, 39, 119, 121, 41, 125
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OFFSET
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0,2
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COMMENTS
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The numerators are given in A056616.
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LINKS
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FORMULA
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a(n) = denominator(r(n)) with r(n) = binomial(2*n,n)/(2*n+1)).
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EXAMPLE
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The rationals r(n) begin: 1, 2/3, 6/5, 20/7, 70/9, 252/11, 924/13, 1144/5, 12870/17, ...
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MATHEMATICA
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Table[Binomial[2 n, n]/(2 n + 1), {n, 0, 70}]//Denominator (* Harvey P. Dale, May 01 2019 *)
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PROG
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(Magma) [Denominator((Binomial (2*n, n)) / (2*n + 1)): n in [0..70]]; // Vincenzo Librandi, May 27 2019
(PARI) a(n) = denominator(binomial(2*n, n) / (2*n+1)); \\ Michel Marcus, May 27 2019
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CROSSREFS
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KEYWORD
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nonn,easy,frac
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AUTHOR
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STATUS
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approved
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