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A172087 Main pure Bernoulli twin numbers (fourth part; see A027641, A172083, A172086): denominators. Also double A001897. 4
1, 1, 3, 3, 15, 15, 21, 21, 15, 15, 33, 33, 1365, 1365, 3, 3, 255, 255, 399, 399, 165, 165, 69, 69, 1365, 1365, 3, 3, 435, 435, 7161, 7161, 255, 255, 3, 3, 959595, 959595, 3, 3, 6765, 6765, 903, 903, 345, 345, 141, 141 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Main pure Bernoulli twin numbers are 2,-2,1/3,-1/3,-1/15,1/15,1/21,-1/21,-1/15,1/15,5/33,-5/33,. Numerators are A172086: 2,-2,1,-1,-1,1,. Also reduced (2*A000367/A002445=2,-2,2/6,-2/6,-2/30,2/42,-2/42,-2/30,2/30,).

LINKS

Table of n, a(n) for n=0..47.

MATHEMATICA

b[n_] := -2*(2^(2*n - 1) - 1)*BernoulliB[2*n]; t = Table[b[n], {n, 0, 30}] // Denominator; A172087 = Transpose[{t, t}] // Flatten (* Jean-François Alcover, Jan 11 2016 *)

CROSSREFS

Sequence in context: A280840 A212200 A333862 * A086116 A100735 A129356

Adjacent sequences:  A172084 A172085 A172086 * A172088 A172089 A172090

KEYWORD

nonn

AUTHOR

Paul Curtz, Jan 25 2010

EXTENSIONS

More terms from Jean-François Alcover, Jan 11 2016

STATUS

approved

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Last modified July 5 23:36 EDT 2020. Contains 335475 sequences. (Running on oeis4.)