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.

A135593 Number of n X n symmetric (0,1)-matrices with exactly n+1 entries equal to 1 and no zero rows or columns.

Table of values

n a(n)
2 2
3 9
4 36
5 140
6 540
7 2142
8 8624
9 35856
10 152280
11 666380
12 2982672
13 13716144
14 64487696
15 310693320
16 1528801920
17 7691652992
18 39474925344
19 206758346256
20 1103332900160
21 5999356762560
22 33197323465152
23 186925844947424
24 1069977071943936

List of values

[2, 9, 36, 140, 540, 2142, 8624, 35856, 152280, 666380, 2982672, 13716144, 64487696, 310693320, 1528801920, 7691652992, 39474925344, 206758346256, 1103332900160, 5999356762560, 33197323465152, 186925844947424, 1069977071943936]

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

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