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A091725 Decimal expansion of second exponential integral at 1, ExpIntegralEi[1]. 40
1, 8, 9, 5, 1, 1, 7, 8, 1, 6, 3, 5, 5, 9, 3, 6, 7, 5, 5, 4, 6, 6, 5, 2, 0, 9, 3, 4, 3, 3, 1, 6, 3, 4, 2, 6, 9, 0, 1, 7, 0, 6, 0, 5, 8, 1, 7, 3, 2, 7, 0, 7, 5, 9, 1, 6, 4, 6, 2, 2, 8, 4, 3, 1, 8, 8, 2, 5, 1, 3, 8, 3, 4, 5, 3, 3, 8, 0, 4, 1, 5, 3, 5, 4, 8, 9, 0, 0, 7, 1, 0, 1, 2, 6, 1, 3, 8, 9, 5, 6, 9, 7, 1, 8, 1 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Robert Price, Table of n, a(n) for n = 1..10000

Zbigniew Gołębiewski, Mateusz Klimczak, Protection Number of Recursive Trees, 2019 Proceedings of the Sixteenth Workshop on Analytic Algorithmics and Combinatorics (ANALCO).

Eric Weisstein's World of Mathematics, Exponential Integral

Eric Weisstein's World of Mathematics, Factorial Sums

Eric Weisstein's World of Mathematics, Logarithmic Integral

FORMULA

Equals li(e), where li(x) is the logarithmic integral, and gamma + Sum_{n>=1} 1/(n*n!) = A001620 + A229837. - Amiram Eldar, Mar 05 2019

EXAMPLE

1.89511781635593675546652...

MATHEMATICA

RealDigits[ExpIntegralEi[1], 10, 105][[1]] (* Robert G. Wilson v, Oct 08 2004 *)

PROG

(PARI) real(-eint1(-1)) \\ Charles R Greathouse IV, Apr 23 2013

CROSSREFS

Cf. A001563, A001620, A229837.

Sequence in context: A243267 A243268 A203071 * A029689 A201294 A199383

Adjacent sequences: A091722 A091723 A091724 * A091726 A091727 A091728

KEYWORD

nonn,cons

AUTHOR

Eric W. Weisstein, Feb 01 2004

STATUS

approved

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Last modified December 7 22:27 EST 2022. Contains 358671 sequences. (Running on oeis4.)