A321840 - OEIS

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.

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

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OFFSET

4,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 4..150

CROSSREFS

Column k=4 of A257783.

Sequence in context: A250577 A242844 A185445 * A052759 A356911 A353229

Adjacent sequences: A321837 A321838 A321839 * A321841 A321842 A321843

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Nov 19 2018

STATUS

approved