OFFSET
1,1
REFERENCES
Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 4.6 Fransén-Robinson constant, p. 263.
LINKS
Eric Weisstein's MathWorld, Fransén-Robinson Constant
FORMULA
Also equals e - Integral_{-oo..oo} e^(-e^x)/(x^2 + Pi^2) dx (observed by Ramanujan).
EXAMPLE
2.266534507699848835071963857678220918408829714280222193861...
MATHEMATICA
NIntegrate[1/Gamma[1 + x], {x, 0, Infinity}, WorkingPrecision -> 104] // RealDigits // First
PROG
(Python)
from mpmath import *
mp.dps = 200
A247377 = [d for d in nstr(quad(lambda x:1/gamma(1+x), [0, inf]), n=mp.dps)[:-1] if d != '.'] # Chai Wah Wu, Sep 16 2014
(PARI)
localprec(100); intnum(x=0, [[1], 1], 1/gamma(1+x)) \\ Dumitru Damian, Oct 12 2023
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Jean-François Alcover, Sep 15 2014
STATUS
approved