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Lindley equation
In probability theory, the Lindley equation, Lindley recursion or Lindley process is a discrete-time stochastic process An where n takes integer values and: An + 1 = max(0, An + Bn). Processes of this form can be used to describe the waiting time of customers in a queue or evolution of a queue length over time. The idea was first proposed in the discussion following Kendall's 1951 paper.