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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.

A209991 Number of 2 X 2 matrices with all elements in {0,1,...,n} and determinant in {0,1}.

Table of values

n a(n)
0 1
1 13
2 38
3 79
4 136
5 209
6 302
7 407
8 536
9 681
10 846
11 1015
12 1240
13 1441
14 1678
15 1951
16 2240
17 2505
18 2854
19 3151
20 3552
21 3945
22 4326
23 4687
24 5216
25 5657
26 6110
27 6615
28 7192
29 7649
30 8342
31 8831
32 9472
33 10105
34 10702
35 11407
36 12272
37 12857
38 13526
39 14279
40 15224

List of values

[1, 13, 38, 79, 136, 209, 302, 407, 536, 681, 846, 1015, 1240, 1441, 1678, 1951, 2240, 2505, 2854, 3151, 3552, 3945, 4326, 4687, 5216, 5657, 6110, 6615, 7192, 7649, 8342, 8831, 9472, 10105, 10702, 11407, 12272, 12857, 13526, 14279, 15224]

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

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