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A168059
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Denominator of (n+2)/(n*(n+1)).
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2
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2, 3, 12, 10, 30, 21, 56, 36, 90, 55, 132, 78, 182, 105, 240, 136, 306, 171, 380, 210, 462, 253, 552, 300, 650, 351, 756, 406, 870, 465, 992, 528, 1122, 595, 1260, 666, 1406, 741, 1560, 820, 1722, 903, 1892, 990, 2070, 1081, 2256, 1176, 2450, 1275, 2652, 1378
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OFFSET
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1,1
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LINKS
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G. C. Greubel, Table of n, a(n) for n = 1..1000
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FORMULA
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From R. J. Mathar, Nov 18 2009: (Start)
a(n) = 3*a(n-2) - 3*a(n-4) + a(n-6).
G.f.: x*(2+3*x+6*x^2+x^3)/((1-x)^3*(1+x)^3).
a(2n+1) = A002939(n+1).
a(2n) = A014105(n). (End)
a(n) = lcm(n+1, binomial(n+1,2)). - Enrique Pérez Herrero, Mar 13 2012
From Ilya Gutkovskiy, Jul 08 2016: (Start)
E.g.f.: x*(x + 1)*sinh(x) + x*(x + 4)*cosh(x)/2.
a(n) = n*(n + 1)*(3 - (-1)^n)/4.
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EXAMPLE
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a(4)=10 because 6/(5*4) = 3/10 has 10 in the denominator.
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MATHEMATICA
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Table[Denominator[(n+2)/(n+1)/n], {n, 60}]
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PROG
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(PARI) a(n) = denominator((n+2)/(n*(n+1))); \\ Michel Marcus, Jul 09 2016
(MAGMA) [Lcm(n+1, Binomial(n+1, 2)): n in [1..60]]; // Vincenzo Librandi, Mar 13 2018
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CROSSREFS
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Numerator is in A026741.
Sequence in context: A079077 A027611 A303221 * A068550 A093432 A212303
Adjacent sequences: A168056 A168057 A168058 * A168060 A168061 A168062
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KEYWORD
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nonn,frac,easy
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AUTHOR
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Vladimir Joseph Stephan Orlovsky, Nov 17 2009
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STATUS
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approved
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