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) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 120 |
| 6 | 720 |
| 7 | 4620 |
| 8 | 33600 |
| 9 | 276192 |
| 10 | 2540160 |
| 11 | 25874640 |
| 12 | 289301760 |
| 13 | 3523208832 |
| 14 | 46425899520 |
| 15 | 658169366400 |
| 16 | 9988896153600 |
| 17 | 161590513766400 |
| 18 | 2775695618949120 |
| 19 | 50455787382604800 |
| 20 | 967644983144448000 |