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.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 68 |
| 5 | 720 |
| 6 | 9804 |
| 7 | 163184 |
| 8 | 3210192 |
| 9 | 72870120 |
| 10 | 1874721360 |
| 11 | 53905894152 |
| 12 | 1713195438624 |
| 13 | 59633476003920 |
| 14 | 2256257009704320 |
| 15 | 92196226214092800 |
| 16 | 4046446853549201664 |
| 17 | 189845257963376620800 |
| 18 | 9481546020840245199360 |
| 19 | 502242773970728703225600 |
| 20 | 28124368575613839072714240 |