151996648798domain: NAppears in sequencesNumber of words w of length n such that each letter of the quaternary alphabet is used at least once and for every prefix z of w we have #(z,a_i) = 0 or #(z,a_i) >= #(z,a_j) for all j>i and #(z,a_i) counts the occurrences of the i-th letter in z.at n=19A321840