1. A method for determining a rule which governs the generation of a string of integers, comprising the steps of: generating an input string of integers; initially generating a set of trial programs for use in generating a set of trial integer sequences, each of said programs corresponding to a predetermined integer generating rule; running said set of trial programs to generate a corresponding set of trial integer sequences; comparing said input string of integers with each of said trial integer sequences and for generating an error measure corresponding to the difference therebetween; and, selecting which program in said set of trial programs executes, the execution of which results in the generation of an integer sequence most closely approximating said input integer string, thereby to identify the rule which governs the generation of said input string of integers.