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A264389 Denominator of binomial(n-1, 2)/(6*n), for n >= 1.  Denominator of Dedekind sum s(1,n). 6
1, 1, 18, 8, 5, 18, 14, 16, 27, 5, 22, 72, 13, 14, 90, 32, 17, 27, 38, 40, 63, 22, 46, 144, 25, 13, 162, 56, 29, 90, 62, 64, 99, 17, 70, 216, 37, 38, 234, 80, 41, 63, 86, 88, 135, 46, 94, 288, 49, 25, 306, 104, 53, 162, 110, 112, 171, 29, 118, 360, 61, 62, 378 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

See A264388 for the numerators and details about the Dedekind sum s(1,n), as well as references.

LINKS

Table of n, a(n) for n=1..63.

FORMULA

a(n) = denominator(binomial(n-1, 2)/(6*n)), n >= 1.

a(n) = denominator(s(1,n)), with s(1,n) = Sum_{r=1..(n-1)} (r/n)*(r/n - floor(r/n)- 1/2), n >= 1, where s(h,k) are the Dedekind sums.

MATHEMATICA

Denominator[Table[Binomial[n-1, 2]/(6n), {n, 50}]] (* Harvey P. Dale, Aug 30 2016 *)

PROG

(Julia)

using Nemo

A264389(n) = denominator(dedekind_sum(1, n))

[A264389(n) for n in 1:70] |> println # Peter Luschny, Mar 13 2018

CROSSREFS

Cf. A264388.

Sequence in context: A097534 A040310 A068610 * A104218 A033338 A169736

Adjacent sequences:  A264386 A264387 A264388 * A264390 A264391 A264392

KEYWORD

nonn,easy,frac

AUTHOR

Wolfdieter Lang, Jan 11 2016

STATUS

approved

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Last modified September 15 16:44 EDT 2019. Contains 327078 sequences. (Running on oeis4.)