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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
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
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Oct 26 2018
STATUS
approved

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Last modified June 12 20:44 EDT 2024. Contains 373360 sequences. (Running on oeis4.)