The Free On-line Dictionary of Computing (30 December 2018):

pseudorandom number
random number

    One of a sequence of numbers generated by some
   algorithm so as to have an even distribution over some range
   of values and minimal correlation between successive
   values.

   Pseudorandom numbers are used in simulation and
   encryption.  They are pseudorandom not random because the
   sequence eventually repeats exactly and is entirely determined
   by the initial conditions.

   One of the simplest algorithms is

   	x[i+1] = (a * x[i] + c) mod m

   but this repeats after at most m numbers and successive
   numbers are closely related.  Better algorithms generally use
   more previous numbers to calculate the next number.

   (http://random.mat.sbg.ac.at/).

   (2007-06-29)