n-ary mekso operator: Logistical growth/cumulative function, sigmoid function; (X3 / (1 + e^(-X.
X1 is the main independent variable. e is the natural base (te'o); X1 is the primary input, all other Xi's are parameters. Contextless default values: X2 = 1, X3 = 1, X4 = 0, X5 = 0. For the sake of clarity (in case the TeX does not render), the function is: (X3 / (1 + e^(-X.