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A321038 Number of words of length 3n such that all letters of the octonary 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
43263, 7104240, 694377450, 52825297536, 3463906615356, 206132702914710, 11470240358743842, 608199451197152100, 31120996552066805175, 1550313320809537870320, 75665062766954753664390, 3635046065217379316477688, 172499755061750807257325550 (list; graph; refs; listen; history; text; internal format)
OFFSET

8,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 8..602

MAPLE

b:= (n, k)-> `if`(n=0, 1, k/n*add(binomial(3*n, j)*(n-j)*(k-1)^j, j=0..n-1)):

a:= n-> (k-> add((-1)^i*b(n, k-i)/(i!*(k-i)!), i=0..k))(8):

seq(a(n), n=8..25);

CROSSREFS

Column k=8 of A256311.

Sequence in context: A238595 A205053 A146074 * A256767 A258677 A184382

Adjacent sequences:  A321035 A321036 A321037 * A321039 A321040 A321041

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Oct 26 2018

STATUS

approved

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Last modified November 24 18:11 EST 2020. Contains 338616 sequences. (Running on oeis4.)