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 | 4929 |
| 8 | 38544 |
| 9 | 338904 |
| 10 | 3309120 |
| 11 | 35521200 |
| 12 | 415704960 |
| 13 | 5271197205 |
| 14 | 71977504692 |
| 15 | 1053008012790 |
| 16 | 16431803844480 |
| 17 | 272435676775200 |
| 18 | 4782657847248000 |
| 19 | 88624515772410633 |
| 20 | 1728678866577622920 |
| 21 | 35404942557640528620 |
| 22 | 759655818204633900000 |