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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
OFFSET
0,1
REFERENCES
Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 5.6 Otter's tree enumeration constants, p. 303.
LINKS
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
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
Sequence in context: A301817 A011300 A222068 * A157292 A159828 A131114
KEYWORD
nonn,cons
AUTHOR
STATUS
approved