cp's OEIS Frontend

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.

A289312 The number of upper-triangular matrices with integer entries whose absolute sum is equal to n, and each row and column contains at least one nonzero entry.

Table of values

n a(n)
0 1
1 2
2 6
3 26
4 142
5 946
6 7446
7 67658
8 697118
9 8031586
10 102312486
11 1427905658
12 21666671534
13 355138949394
14 6253348428598
15 117720540700842
16 2359368991571518
17 50157679523340994
18 1127327559500923974
19 26709016625807923418
20 665292778385210384078

List of values

[1, 2, 6, 26, 142, 946, 7446, 67658, 697118, 8031586, 102312486, 1427905658, 21666671534, 355138949394, 6253348428598, 117720540700842, 2359368991571518, 50157679523340994, 1127327559500923974, 26709016625807923418, 665292778385210384078]

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

Content is available under The OEIS End-User License Agreement.