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A321840
Number 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.
2
24, 60, 210, 609, 1961, 5952, 19255, 60812, 200281, 652011, 2185981, 7283988, 24809651, 84207955, 290756694, 1001820292, 3500030779, 12211804429, 43101225586, 151996648798, 541273095677, 1926487411495, 6914504463171, 24808989286716, 89666142346093
OFFSET
4,1
LINKS
CROSSREFS
Column k=4 of A257783.
Sequence in context: A250577 A242844 A185445 * A052759 A356911 A353229
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 19 2018
STATUS
approved