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 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 24 |
| 6 | 120 |
| 7 | 720 |
| 8 | 5040 |
| 9 | 40320 |
| 10 | 362880 |
| 11 | 1814400 |
| 12 | 13305600 |
| 13 | 119750400 |
| 14 | 1245404160 |
| 15 | 14529715200 |
| 16 | 186810624000 |
| 17 | 2615348736000 |
| 18 | 39520825344000 |
| 19 | 640237370572800 |
| 20 | 6082255020441600 |
| 21 | 81096733605888000 |
| 22 | 1277273554292736000 |
| 23 | 22480014555552153600 |