A226121 - OEIS

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A226121

Decimal expansion of sum_{n=1..infinity} n^3/(exp(2*Pi*n/13)-1).

1, 1, 9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 5, 9, 3, 7, 4, 5, 8, 5, 1, 0, 2, 5, 5, 4, 7, 3, 3, 5, 5, 8, 8, 5, 8, 4, 9, 1, 3, 3, 9, 7, 3, 8, 4, 1, 5, 0, 4, 3, 3, 9, 1, 5, 8, 0, 5, 4, 1, 2, 7, 9, 3, 5, 1, 5, 8, 7, 8, 5, 1, 6, 5, 4, 2, 3, 2

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OFFSET

3,3

COMMENTS

An almost-integer discovered by Simon Plouffe. The computed sum equals 119 within 31 digits after the decimal point.

LINKS

Table of n, a(n) for n=3..102.

Simon Plouffe, Simon Plouffe Home Page

Eric Weisstein's MathWorld, Almost Integer

EXAMPLE

119.0000000000000000000000000000000959374585102554733558858491339738415043391...

MATHEMATICA

NSum[n^3/(Exp[2*Pi*n/13] - 1), {n, 1, Infinity}, NSumTerms -> 500, WorkingPrecision -> 100] // RealDigits[#, 10, 100] & // First

CROSSREFS

Cf. A060295 (a famous almost-integer: Ramanujan's constant), A226120 (another surprising almost-integer by Simon Plouffe).

Sequence in context: A272826 A019440 A085276 * A337127 A193581 A270034

Adjacent sequences: A226118 A226119 A226120 * A226122 A226123 A226124

KEYWORD

nonn,cons

AUTHOR

Jean-François Alcover, May 27 2013

EXTENSIONS

Offset corrected by Rick L. Shepherd, Jan 01 2014

STATUS

approved