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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 4859 |
| 8 | 37424 |
| 9 | 323784 |
| 10 | 3107520 |
| 11 | 32749200 |
| 12 | 376929246 |
| 13 | 4698101279 |
| 14 | 63058148792 |
| 15 | 906829731450 |
| 16 | 13911580276800 |
| 17 | 226738605155619 |
| 18 | 3912973221007668 |
| 19 | 71280397766349665 |
| 20 | 1366816300552776920 |
| 21 | 27519285653572655340 |
| 22 | 580456044040809459821 |