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A131137 Denominator of (exponential) expansion of log((2*x/3-1)/(x-1)). 3
1, 3, 9, 27, 27, 81, 243, 243, 729, 2187, 729, 2187, 6561, 6561, 19683, 59049, 59049, 177147, 531441, 177147, 531441, 1594323, 1594323, 4782969, 14348907, 14348907, 43046721, 129140163, 14348907, 43046721, 129140163, 129140163, 387420489 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(n) = 3^A131138(n).

Also, starting at second term, denominator of (1-(2/3)^n)*(n-1)!;

Conjecture: starting at third term, also equals the denominator of polylog(-n,1/4)/4. - Wouter Meeussen, Feb 13 2014

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

MATHEMATICA

Denominator[CoefficientList[Series[Log[(2 x/3 - 1)/(x - 1)], {x, 0, 32}], x] Range[0, 32]!]; (* or *) Prepend[Table[Denominator[(1 - (2/3)^n) (n - 1)!], {n, 32}], 1]; (* or *) Join[{1, 3}, Table[Denominator[PolyLog[-n, 1/4]/4 ], {n, 31}]] (* Wouter Meeussen, Feb 13 2014 *)

PROG

(PARI) a(n)=if(n<4, 3^n, denominator(polylog(1-n, 1/4)/4)) \\ Charles R Greathouse IV, Jul 15 2014

CROSSREFS

Cf. A131136.

Sequence in context: A168427 A070344 A070357 * A061948 A018644 A111117

Adjacent sequences:  A131134 A131135 A131136 * A131138 A131139 A131140

KEYWORD

nonn,easy

AUTHOR

Paul Barry, Jun 17 2007

STATUS

approved

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Last modified April 23 06:08 EDT 2019. Contains 322381 sequences. (Running on oeis4.)