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A256501 Decimal expansion of the positive solution to x = 4*(1-exp(-x)). 4
3, 9, 2, 0, 6, 9, 0, 3, 9, 4, 8, 7, 2, 8, 8, 6, 3, 4, 3, 5, 6, 0, 8, 9, 1, 3, 5, 2, 6, 1, 3, 5, 3, 6, 2, 2, 0, 5, 2, 5, 6, 2, 7, 3, 7, 1, 2, 0, 7, 9, 8, 4, 5, 3, 0, 4, 0, 1, 1, 7, 5, 0, 0, 5, 7, 9, 0, 5, 0, 5, 6, 4, 8, 3, 6, 6, 7, 0, 5, 7, 5, 7, 4, 3, 3, 6, 5, 6, 6, 0, 1, 8, 9, 4, 8, 3, 6, 5, 8, 9, 0, 4, 7, 3, 0 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Each of the positive solutions to x = q*(1-exp(-x)) obtained for q = 2, 3, 4, and 5, appears in several formulas pertinent to the Planck's black-body radiation law. For a given q, the solution can be also written as q+W(-q/exp(q)), where W is the Lambert function. Here q = 4.

LINKS

Stanislav Sykora, Table of n, a(n) for n = 1..2000

SpectralCalc, Calculation of Blackbody Radiance, Appendix C.

Wikipedia, Planck's law

EXAMPLE

3.9206903948728863435608913526135362205256273712079845304011750...

MATHEMATICA

RealDigits[x/.FindRoot[x==4(1-Exp[-x]), {x, 3}, WorkingPrecision->120]] [[1]] (* Harvey P. Dale, May 08 2017 *)

PROG

(PARI) a4=solve(x=0.1, 10, x-4*(1-exp(-x))) \\ Use real precision in excess

CROSSREFS

Cf. A094090 (q=5), A194567 (q=3), A256500 (q=2).

Sequence in context: A128753 A179430 A016048 * A229099 A021259 A194807

Adjacent sequences:  A256498 A256499 A256500 * A256502 A256503 A256504

KEYWORD

nonn,cons

AUTHOR

Stanislav Sykora, Apr 01 2015

STATUS

approved

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Last modified July 26 08:24 EDT 2017. Contains 289799 sequences.