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.

A002137 Number of n X n symmetric matrices with nonnegative integer entries, trace 0 and all row sums 2.

Table of values

n a(n)
0 1
1 0
2 1
3 1
4 6
5 22
6 130
7 822
8 6202
9 52552
10 499194
11 5238370
12 60222844
13 752587764
14 10157945044
15 147267180508
16 2282355168060
17 37655004171808
18 658906772228668
19 12188911634495388
20 237669544014377896
21 4871976826254018760
22 104742902332392298296

List of values

[1, 0, 1, 1, 6, 22, 130, 822, 6202, 52552, 499194, 5238370, 60222844, 752587764, 10157945044, 147267180508, 2282355168060, 37655004171808, 658906772228668, 12188911634495388, 237669544014377896, 4871976826254018760, 104742902332392298296]

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

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