

A321040


Number of words of length 3n such that all letters of the denary alphabet occur at least once and are introduced in ascending order and which can be built by repeatedly inserting triples of identical letters into the initially empty word.


2



1430715, 385671000, 59757446980, 7005490433656, 691555233881785, 60757817462444531, 4909804407096952946, 372791285261732999200, 26986460830582840320825, 1882051044395835159556710, 127426007577261157375345878, 8424538202077517861490125956
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OFFSET

10,1


LINKS

Alois P. Heinz, Table of n, a(n) for n = 10..566


MAPLE

b:= (n, k)> `if`(n=0, 1, k/n*add(binomial(3*n, j)*(nj)*(k1)^j, j=0..n1)):
a:= n> (k> add((1)^i*b(n, ki)/(i!*(ki)!), i=0..k))(10):
seq(a(n), n=10..25);


CROSSREFS

Column k=10 of A256311.
Sequence in context: A054852 A242824 A204288 * A234657 A015361 A259306
Adjacent sequences: A321037 A321038 A321039 * A321041 A321042 A321043


KEYWORD

nonn


AUTHOR

Alois P. Heinz, Oct 26 2018


STATUS

approved



