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A073003 Decimal expansion of -exp(1)*Ei(-1), also called Gompertz's constant, or the Euler-Gompertz constant. 19
5, 9, 6, 3, 4, 7, 3, 6, 2, 3, 2, 3, 1, 9, 4, 0, 7, 4, 3, 4, 1, 0, 7, 8, 4, 9, 9, 3, 6, 9, 2, 7, 9, 3, 7, 6, 0, 7, 4, 1, 7, 7, 8, 6, 0, 1, 5, 2, 5, 4, 8, 7, 8, 1, 5, 7, 3, 4, 8, 4, 9, 1, 0, 4, 8, 2, 3, 2, 7, 2, 1, 9, 1, 1, 4, 8, 7, 4, 4, 1, 7, 4, 7, 0, 4, 3, 0, 4, 9, 7, 0, 9, 3, 6, 1, 2, 7, 6, 0, 3, 4, 4, 2, 3, 7 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

0! - 1! + 2! - 3! + 4! - 5! + ... = (Borel) Sum_{n>=0} (-y)^n n! = KummerU(1,1,1/y)/y.

Decimal expansion of phi(1) where phi(x) = Integral_{t>=0} e^-t/(x+t) dt. - Benoit Cloitre, Apr 11 2003

The divergent series g(x=1,m) = 1^m*1! - 2^m*2! + 3^m*3! - 4^m*4! + ..., m => -1, is intimately related to Gompertz's constant. We discovered that g(x=1,m) = (-1)^m * (A040027(m) - A000110(m+1) * A073003) with A000110 the Bell numbers and A040027 a sequence that was published by Gould, see for more information A163940. - Johannes W. Meijer, Oct 16 2009

REFERENCES

Bruce C. Berndt, Ramanujan's notebooks Part II, Springer, p. 171

Bruce C. Berndt, Ramanujan's notebooks Part I, Springer, p. 144-145.

S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 424-425.

Wall, H. S., Analytic Theory of Continued Fractions, Van Nostrand, New York, 1948, p. 356.

LINKS

Robert Price, Table of n, a(n) for n = 0..10000

A. I. Aptekarev, On linear forms containing the Euler constant, arXiv:0902.1768 [math.NT]. [From R. J. Mathar, Feb 14 2009]

Richard P. Brent, M. L. Glasser, Anthony J. Guttmann, A Conjectured Integer Sequence Arising From the Exponential Integral, arXiv:1812.00316 [math.NT], 2018.

G. H. Hardy, Divergent Series , Oxford University Press, 1949. p. 29. - Johannes W. Meijer, Oct 16 2009

Jeffrey C. Lagarias, Euler's constant: Euler's work and modern developments, arXiv:1303.1856 [math.NT], 2013; Bull. Amer. Math. Soc., 50 (2013), 527-628.

Simon Plouffe, -exp(1)*Ei(-1)

Ed Sandifer, Divergent Series, How Euler Did It, MAA Online, June 2006. - Johannes W. Meijer, Oct 16 2009

Eric Weisstein's World of Mathematics, Gompertz Constant

Eric Weisstein's World of Mathematics, Exponential Integral

FORMULA

phi(1) = e*(Sum_{k>=1} (-1)^(k-1)/(k*k!) - Gamma) = 0.596347362323194... where Gamma is the Euler constant.

G = 0.596347... = 1/(1+1/(1+1/(1+2/(1+2/(1+3/(1+3/(1+4/(1+4/(1+5/(1+5/(1+6/(... - Philippe Deléham, Aug 14 2005

Equals A001113*A099285. - Johannes W. Meijer, Oct 16 2009

From Peter Bala, Oct 11 2012: (Start)

Stieltjes found the continued fraction representation G = 1/(2 - 1^2/(4 - 2^2/(6 - 3^2/(8 - ...)))). See [Wall, Chapter 18, (92.7) with a = 1]. The sequence of convergents to the continued fraction begins [1/2, 4/7, 20/34, 124/209, ...]. The numerators are in A002793 and the denominators in A002720.

Also, 1 - G has the continued fraction representation 1/(3 - 2/(5 - 6/(7 - ... -n*(n+1)/((2*n+3) - ...)))) with convergents beginning [1/3, 5/13, 29/73, 201/501, ...]. The numerators are in A201203 (unsigned) and the denominators are in A000262.

(End)

G = f(1) with f solution to the o.d.e. x^2*f'(x) + (x+1)*f(x)=1 such that f(0)=1. - Jean-François Alcover, May 28 2013

EXAMPLE

0.59634736232319407434107849936927937607417786015254878157348491...

MATHEMATICA

RealDigits[N[-Exp[1]*ExpIntegralEi[-1], 105]][[1]]

G = 1/Fold[Function[2*#2 - #2^2/#1], 2, Reverse[Range[10^4]]] // N[#, 105]&; RealDigits[G] // First (* Jean-François Alcover, Sep 19 2014 *)

PROG

(PARI) eint1(1)*exp(1) \\ Charles R Greathouse IV, Apr 23 2013

(MAGMA) SetDefaultRealField(RealField(100)); ExponentialIntegralE1(1)*Exp(1); // G. C. Greubel, Dec 04 2018

(Sage) numerical_approx(exp_integral_e(1, 1)*exp(1), digits=100) # G. C. Greubel, Dec 04 2018

CROSSREFS

Cf. A001620, A000262, A002720, A002793, A153229, A201203.

Sequence in context: A051158 A117605 A303983 * A087498 A274633 A238200

Adjacent sequences:  A073000 A073001 A073002 * A073004 A073005 A073006

KEYWORD

cons,nonn,changed

AUTHOR

Robert G. Wilson v, Aug 03 2002

EXTENSIONS

Additional references from Gerald McGarvey, Oct 10 2005

Link corrected by Johannes W. Meijer, Aug 01 2009

STATUS

approved

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Last modified December 19 02:36 EST 2018. Contains 318245 sequences. (Running on oeis4.)