where Yj is the sequence of vertexes, Nj is the number of pattern occurrences in the sequence Y1...Yj (or X = X1...Xj as it is the same), where f is the final (absorbing state) and where a ∈ ℕ is the observed number of occurrences Nobs if the pattern is over-represented and Nobs + 1 if it is under-represented.