By integrating along the Hankel contour, the contour integral expression of the Gamma function becomes . References Further reading Schmelzer, Thomas; Trefethen, Lloyd N. (2007-01). "Computing the Gamma Function Using Contour Integrals and Rational Approximations". SIAM Journal on Numerical Analysis. 45 (2): 558–571. . . Hugh L. Montgomery; Robert C. Vaughan (2007). Multiplicative number theory I. Classical theory. Cambridge tracts in advanced mathematics. 97. p. 515. . External links http://mathworld.wolfram.com/HankelContour.html NIST Digital Library of Mathematical Functions:Gamma Function:Integral Representation Complex analysis Special functions