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A244641 Decimal expansion of the sum of the reciprocals of the pentagonal numbers (A000326). 2
1, 4, 8, 2, 0, 3, 7, 5, 0, 1, 7, 7, 0, 1, 1, 1, 2, 2, 3, 5, 9, 1, 6, 5, 7, 4, 5, 3, 1, 2, 5, 4, 2, 1, 3, 8, 1, 6, 5, 8, 4, 0, 5, 4, 2, 5, 3, 7, 5, 5, 0, 7, 7, 7, 9, 6, 3, 4, 1, 9, 8, 0, 6, 5, 5, 2, 4, 3, 5, 9, 6, 9, 8, 5, 2, 9, 4, 7, 3, 0, 1, 6, 9, 3, 6, 7, 2, 2, 2, 7, 6, 2, 2, 9, 1, 3, 6, 0, 9, 7, 5, 0, 7, 6, 8 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..105.

Hongwei Chen and G. C. Greubel, Sum of the Reciprocals of Polygonal Numbers (Solved), SIAM Problems and solutions.

FORMULA

Sum_{n>=1} 2/(3n^2-n).

Equals 3*log(3) - Pi*sqrt(3)/3 = A016650 - A093602. - Michel Marcus, Jul 03 2014

EXAMPLE

1.482037501770111223591657453125421381658405425375507779634198065524359698529473...

MATHEMATICA

RealDigits[ Sum[2/(3 n^2 - n), {n, 1, Infinity}], 10, 111][[1]]

CROSSREFS

Cf. A000038, A013661, A016627, A016650, A093602, A244639, A244645, A275792.

Sequence in context: A248415 A295086 A134484 * A274192 A021958 A200412

Adjacent sequences:  A244638 A244639 A244640 * A244642 A244643 A244644

KEYWORD

nonn,cons,easy

AUTHOR

Robert G. Wilson v, Jul 03 2014

STATUS

approved

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Last modified April 22 21:39 EDT 2018. Contains 302916 sequences. (Running on oeis4.)