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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A257783 Number T(n,k) of words w of length n such that each letter of the k-ary alphabet is used at least once 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; triangle T(n,k), n>=0, 0<=k<=n, read by rows.

Table of values

n a(n)
0 1
1 0
2 1
3 0
4 1
5 2
6 0
7 1
8 3
9 6
10 0
11 1
12 7
13 12
14 24
15 0
16 1
17 12
18 35
19 60
20 120
21 0
22 1
23 25
24 87
25 210
26 360
27 720
28 0
29 1
30 44
31 232
32 609
33 1470
34 2520
35 5040
36 0
37 1
38 89
39 599
40 1961
41 4872
42 11760
43 20160
44 40320
45 0
46 1
47 160
48 1591
49 5952
50 17649
51 43848
52 105840
53 181440
54 362880
55 0
56 1
57 321
58 4202
59 19255
60 60465
61 176490
62 438480
63 1058400
64 1814400
65 3628800

List of values

[1, 0, 1, 0, 1, 2, 0, 1, 3, 6, 0, 1, 7, 12, 24, 0, 1, 12, 35, 60, 120, 0, 1, 25, 87, 210, 360, 720, 0, 1, 44, 232, 609, 1470, 2520, 5040, 0, 1, 89, 599, 1961, 4872, 11760, 20160, 40320, 0, 1, 160, 1591, 5952, 17649, 43848, 105840, 181440, 362880, 0, 1, 321, 4202, 19255, 60465, 176490, 438480, 1058400, 1814400, 3628800]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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