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A168059 Denominator of (n+2)/(n*(n+1)). 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..1000

FORMULA

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.

EXAMPLE

a(4)=10 because 6/(5*4) = 3/10 has 10 in the denominator.

MATHEMATICA

Table[Denominator[(n+2)/(n+1)/n], {n, 60}]

PROG

(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

CROSSREFS

Numerator is in A026741.

Sequence in context: A079077 A027611 A303221 * A068550 A093432 A212303

Adjacent sequences:  A168056 A168057 A168058 * A168060 A168061 A168062

KEYWORD

nonn,frac,easy

AUTHOR

Vladimir Joseph Stephan Orlovsky, Nov 17 2009

STATUS

approved

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Last modified January 24 22:09 EST 2021. Contains 340414 sequences. (Running on oeis4.)