【欧拉-马斯刻若尼常数】
欧拉-马斯刻若尼常数是一个数学常数，定义为调和级数与自然对数的差值：
它的近似值为，
欧拉-马斯刻若尼常数主要应用于数论。
== 历史 ==
该常数最先由瑞士数学家莱昂哈德·欧拉在1735年发表的文章De Progressionibus harmonicus observationes中定义。欧拉曾经使用作为它的符号，并计算出了它的前6位小数。1761年他又将该值计算到了16位小数。1790年，意大利数学家洛伦佐·马斯凯罗尼引入了作为这个常数的符号，并将该常数计算到小数点后32位。但后来的计算显示他在第20位的时候出现了错误。
目前尚不知道该常数是否为有理数，但是分析表明如果它是一个有理数，那么它的分母位数将超过10242080。
== 性质 ==
=== 与伽玛函数的关系 ===
。
。
。
=== 与ζ函数的关系 ===
。
:。
:
:。
=== 积分 ===
:
:
。
=== 级数展开式 ===
.
的连分数展开式为：
id=A002852.
=== 渐近展开式 ===
== 已知位数 ==
== 相关证明 ==
== 参考文献 ==
# Derives γ as sums over Riemann zeta functions.
#Gourdon, Xavier, and Sebah, P. (2002) " Collection of formulas for Euler's constant, γ. date=20091212002936 "
#Gourdon, Xavier, and Sebah, P. (2004) " The Euler constant: γ. date=20090428001402 "
#Donald Knuth (1997) The Art of Computer Programming, Vol. 1, 3rd ed. Addison-Wesley. ISBN 978-0-201-89683-1
#Krämer, Stefan (2005) Die Eulersche Konstante γ und verwandte Zahlen. Diplomarbeit, Universität Göttingen.
#Sondow, Jonathan (1998) " An antisymmetric formula for Euler's constant," Mathematics Magazine 71: 219-220.
#Sondow, Jonathan (2002) " A hypergeometric approach, via linear forms involving logarithms, to irrationality criteria for Euler's constant." With an Appendix by  Sergey Zlobin, Mathematica Slovaca 59: 307-314.
# title= An infinite product for eγ via hypergeometric formulas for Euler's constant, γ
#Sondow, Jonathan (2003a) " Criteria for irrationality of Euler's constant," Proceedings of the American Mathematical Society 131: 3335-3344.
#Sondow, Jonathan (2005) " Double integrals for Euler's constant and ln 4/π and an analog of Hadjicostas's formula," American Mathematical Monthly 112: 61-65.
#Sondow, Jonathan (2005)  "New Vacca-type rational series for Euler's constant and its 'alternating' analog ln 4/π."
# title= Euler's constant, q-logarithms, and formulas of Ramanujan and Gosper Ramanujan Journal 12: 225-244.
#G. Vacca (1926), "Nuova serie per la costante di Eulero, C = 0,577…". Rendiconti, Accademia Nazionale dei Lincei, Roma, Classe di Scienze Fisiche, Matematiche e Naturali (6) 3, 19–20.
#James Whitbread Lee Glaisher (1872), "On the history of Euler's constant". Messenger of Mathematics. New Series, vol.1, p. 25-30, JFM 03.0130.01
#Carl Anton Bretschneider (1837). "Theoriae logarithmi integralis lineamenta nova". Crelle Journal, vol.17, p. 257-285 (submitted 1835)
#Lorenzo Mascheroni (1790). "Adnotationes ad calculum integralem Euleri, in quibus nonnulla problemata ab Eulero proposita resolvuntur". Galeati, Ticini.
#Lorenzo Mascheroni (1792). "Adnotationes ad calculum integralem Euleri. In quibus nonnullae formulae ab Eulero propositae evolvuntur". Galeati, Ticini. Both online at: http://books.google.de/books?id=XkgDAAAAQAAJ date=20121024193226
#
#year=1991
#E.A. Karatsuba, On the computation of the Euler constant γ, J. of Numerical Algorithms Vol.24, No.1-2, pp. 83–97 (2000)
#M. Lerch, Expressions nouvelles de la constante d'Euler. Sitzungsberichte der Königlich Böhmischen Gesellschaft der Wissenschaften 42, 5 p. (1897)
#  eprint=1303.1856, Bulletin of the American Mathematical Society 50 (4): 527-628 (2013)
== 外部连结 ==
*title=Euler-Mascheroni constant
*Krämer, Stefan " Euler's Constant γ=0.577... Its Mathematics and History."
* Jonathan Sondow.
* Fast Algorithms and the FEE Method date=20210402055902 , E.A. Karatsuba (2005)
*Further formulae which make use of the constant:  Gourdon and Sebah (2004). date=20091212002936