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A272055 Decimal expansion of -1/(e^2 Ei(-1)), an increasing rooted tree enumeration constant associated with the Euler-Gompertz constant, where Ei is the exponential integral. 1
6, 1, 6, 8, 8, 7, 8, 4, 8, 2, 8, 0, 7, 2, 7, 0, 7, 1, 4, 4, 4, 9, 3, 8, 3, 4, 5, 6, 6, 2, 2, 8, 5, 4, 9, 3, 5, 2, 4, 9, 0, 0, 5, 6, 9, 3, 3, 1, 6, 8, 8, 1, 7, 8, 6, 5, 6, 6, 1, 0, 3, 3, 2, 3, 1, 9, 1, 4, 3, 7, 2, 4, 2, 5, 1, 5, 4, 7, 6, 7, 2, 7, 3, 0, 3, 3, 9, 8, 2, 5, 6, 0, 3, 1, 4, 9, 4, 8, 3, 4, 5, 1, 1 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,1

REFERENCES

Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 5.6 Otter's tree enumeration constants, p. 303.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..10000

F. Bergeron, Ph. Flajolet and B. Salvy, Varieties of Increasing Trees, Lecture Notes in Computer Science vol. 581, ed. J.-C. Raoult, Springer-Verlag, 1992, pp. 24-48.

Eric Weisstein's MathWorld, Gompertz Constant

Eric Weisstein's MathWorld, Exponential Integral

Eric Weisstein's MathWorld, Rooted Tree

Index entries for sequences related to mobiles

FORMULA

Equals 1 / (e * A073003).

Also equals  -1 / (e^2 * (gamma - Sum_{n>=1} (-1)^(n-1)/(n*n!))), where gamma is the Euler-Mascheroni constant A001620.

EXAMPLE

0.61688784828072707144493834566228549352490056933168817865661...

MATHEMATICA

RealDigits[-1/(E^2*ExpIntegralEi[-1]), 10, 103][[1]]

PROG

(PARI) default(realprecision, 100); 1/(exp(2)*eint1(1)) \\ G. C. Greubel, Sep 07 2018

CROSSREFS

Cf. A029768, A073003.

Sequence in context: A301817 A011300 A222068 * A157292 A159828 A131114

Adjacent sequences:  A272052 A272053 A272054 * A272056 A272057 A272058

KEYWORD

nonn,cons

AUTHOR

Jean-Fran├žois Alcover, Apr 19 2016

STATUS

approved

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Last modified March 28 05:38 EDT 2020. Contains 333073 sequences. (Running on oeis4.)