It is difficult to define what is random in general terms, though it is easier if one constrains the terms to probabilistic set-ups with certain assumed features. Thus, a sequence of n terms - with n considerably larger than 10 - of the 10 digits from 0 to 9 is random if for any i from 1 to n the i-th term has a 1 in 10 probability of being any of the digits and the conditional probability of the i-th term being any specific digit given the foregoing terms is also 1 in 10. (There is more to be said, but this gives the idea.)

There are lists of random numbers in roughly this sense, printed or generated by a computer, which are used for statistical tests of many kinds, for instance to generate random choices.