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 | 1 |
| 1 | 4 |
| 2 | 40 |
| 3 | 288 |
| 4 | 3072 |
| 5 | 23600 |
| 6 | 259200 |
| 7 | 1847104 |
| 8 | 21523360 |
| 9 | 152845056 |
| 10 | 1700870400 |
| 11 | 12550120000 |
| 12 | 130459631616 |
| 13 | 997562438080 |
| 14 | 11159367815680 |
| 15 | 81159501312000 |
| 16 | 926510094425920 |
| 17 | 6670865700716544 |
| 18 | 73205598106368000 |
| 19 | 540340585126398016 |
| 20 | 5691215305506816000 |