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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.

A291971 Triangle read by rows: T(n,k) = 3 * T(n-k,k-1) + T(n-k,k) with T(0,0) = 1 for 0 <= k <= A003056(n).

Table of values

n a(n)
0 1
1 0
2 3
3 0
4 3
5 0
6 3
7 9
8 0
9 3
10 9
11 0
12 3
13 18
14 0
15 3
16 18
17 27
18 0
19 3
20 27
21 27
22 0
23 3
24 27
25 54
26 0
27 3
28 36
29 81
30 0
31 3
32 36
33 108
34 81
35 0
36 3
37 45
38 135
39 81
40 0
41 3
42 45
43 189
44 162
45 0
46 3
47 54
48 216
49 243
50 0
51 3
52 54
53 270
54 405
55 0
56 3
57 63
58 324
59 486
60 243
61 0
62 3
63 63
64 378
65 729
66 243
67 0
68 3
69 72
70 432
71 891

List of values

[1, 0, 3, 0, 3, 0, 3, 9, 0, 3, 9, 0, 3, 18, 0, 3, 18, 27, 0, 3, 27, 27, 0, 3, 27, 54, 0, 3, 36, 81, 0, 3, 36, 108, 81, 0, 3, 45, 135, 81, 0, 3, 45, 189, 162, 0, 3, 54, 216, 243, 0, 3, 54, 270, 405, 0, 3, 63, 324, 486, 243, 0, 3, 63, 378, 729, 243, 0, 3, 72, 432, 891]

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