Thus the autocorrelation between the following numbers
would be of interest.
The value M is the largest integer such that where N is the total number of values in the sequence.
E.g. N = 17, i = 3, m = 4, then the above sequence would be 3, 7, 11, 15 (M = 2). The reason we require M+1 instead of M is that we need to have at least two numbers to test (M = 0) the autocorrelation.