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 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 (list; graph; refs; listen; history; text; internal format)
 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)*(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))(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

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Last modified January 18 03:09 EST 2021. Contains 340249 sequences. (Running on oeis4.)