A213877 Number of words w where each letter of the 7-ary alphabet occurs n times 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.

1, 5040, 135135, 210455470, 1428739165560, 23060727168393236, 668821362774214965294, 29745278219128813035415595, 1835364055105945091130559202709, 146812609193179942830629976945746464, 14506158303190746913523011613729321067580

Offset

0,2

Links

Table of n, a(n) for n=0..10.

Example

a(0) = 1: the empty word.
a(1) = 5040: abcdefg, abcdegf, abcdfeg, ..., gfedbca, gfedcab, gfedcba, (all permutations of 7 letters).
a(2) = 135135: aabbccddeeffgg, aabbccddeefgfg, aabbccddeegffg, ..., gfedcaabbcdefg, gfedcababcdefg, gfedcbaabcdefg.

Crossrefs

Column k=7 of A213275.

Sequence in context: A029575 A179965 A191685 * A135456 A254080 A228910

Adjacent sequences: A213874 A213875 A213876 * A213878 A213879 A213880

Keyword

nonn

Author

Alois P. Heinz, Jun 23 2012

Status

approved