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The gamma function at the imaginary unit i = ... The only values of x > 0 for which Γ(x) = x are x = 1 and x ≈ 3.562 382 285 390 897 691 415 644 3427 ...
The gamma function then is defined in the complex plane as the analytic continuation of this integral function: it is a meromorphic function which is holomorphic except at zero and the negative integers, where it has simple poles. The gamma function has no zeros, so the reciprocal gamma function 1 / Γ(z) is an entire function.
Repeated application of the recurrence relation for the lower incomplete gamma function leads to the power series expansion: [2] (,) = = (+) (+) = = (+ +). Given the rapid growth in absolute value of Γ(z + k) when k → ∞, and the fact that the reciprocal of Γ(z) is an entire function, the coefficients in the rightmost sum are well-defined, and locally the sum converges uniformly for all ...
Thus computing the gamma function becomes a matter of evaluating only a small number of elementary functions and multiplying by stored constants. The Lanczos approximation was popularized by Numerical Recipes , according to which computing the gamma function becomes "not much more difficult than other built-in functions that we take for granted ...
Suppose we wish to generate random variables from Gamma(n + δ, 1), where n is a non-negative integer and 0 < δ < 1. Using the fact that a Gamma(1, 1) distribution is the same as an Exp(1) distribution, and noting the method of generating exponential variables, we conclude that if U is uniformly distributed on (0, 1], then −ln U is ...
The asymptotic expansion of the gamma function, ... 1 −0.0728158454836 A082633: 2 −0.0096903631928 A086279: 3 +0.0020538344203 A086280: 4 +0.0023253700654
Plot of 1 / Γ(x) along the real axis Reciprocal gamma function 1 / Γ(z) in the complex plane, plotted using domain coloring. In mathematics, the reciprocal gamma function is the function = (), where Γ(z) denotes the gamma function.
In mathematics, Spouge's approximation is a formula for computing an approximation of the gamma function. It was named after John L. Spouge, who defined the formula in a 1994 paper. [1] The formula is a modification of Stirling's approximation, and has the form