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 | 1 |
| 3 | 2 |
| 4 | 8 |
| 5 | 48 |
| 6 | 480 |
| 7 | 5760 |
| 8 | 92160 |
| 9 | 2027520 |
| 10 | 48660480 |
| 11 | 1362493440 |
| 12 | 49049763840 |
| 13 | 1961990553600 |
| 14 | 82403603251200 |
| 15 | 3790565749555200 |
| 16 | 197109418976870400 |
| 17 | 11826565138612224000 |
| 18 | 780553299148406784000 |
| 19 | 54638730940388474880000 |
| 20 | 4152543551469524090880000 |
| 21 | 340508571220500975452160000 |