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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.

A131111 T(n, k) = 3*binomial(n,k) - 2*I(n,k), where I is the identity matrix; triangle T read by rows (n >= 0 and 0 <= k <= n).

Table of values

n a(n)
0 1
1 3
2 1
3 3
4 6
5 1
6 3
7 9
8 9
9 1
10 3
11 12
12 18
13 12
14 1
15 3
16 15
17 30
18 30
19 15
20 1
21 3
22 18
23 45
24 60
25 45
26 18
27 1
28 3
29 21
30 63
31 105
32 105
33 63
34 21
35 1
36 3
37 24
38 84
39 168
40 210
41 168
42 84
43 24
44 1
45 3
46 27
47 108
48 252
49 378
50 378
51 252
52 108
53 27
54 1

List of values

[1, 3, 1, 3, 6, 1, 3, 9, 9, 1, 3, 12, 18, 12, 1, 3, 15, 30, 30, 15, 1, 3, 18, 45, 60, 45, 18, 1, 3, 21, 63, 105, 105, 63, 21, 1, 3, 24, 84, 168, 210, 168, 84, 24, 1, 3, 27, 108, 252, 378, 378, 252, 108, 27, 1]

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

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