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 | 5 |
| 3 | 21 |
| 4 | 102 |
| 5 | 480 |
| 6 | 2688 |
| 7 | 14880 |
| 8 | 96480 |
| 9 | 622080 |
| 10 | 4613760 |
| 11 | 34110720 |
| 12 | 285586560 |
| 13 | 2386298880 |
| 14 | 22289541120 |
| 15 | 207921530880 |
| 16 | 2145056256000 |
| 17 | 22108972032000 |
| 18 | 249782787072000 |
| 19 | 2820035699712000 |
| 20 | 34637103857664000 |
| 21 | 425205351825408000 |