Euler-Mascheroni constant

The Euler-Mascheroni Constant is a recurring constant in analysis and number theory.

$\gamma = \lim_{n \to \infty} (-\ln n + \sum_{c=1}^n \frac {1}{c})$

$\approx 0.57721566490153286060651209008240243104215933593992 \ldots$

It is still unknown whether or not this number is rational or irrational and whether or not this number is transcendental.