

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
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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



