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 | 1 |
| 3 | 9 |
| 4 | 48 |
| 5 | 300 |
| 6 | 2520 |
| 7 | 22680 |
| 8 | 282240 |
| 9 | 3265920 |
| 10 | 43545600 |
| 11 | 618710400 |
| 12 | 10298534400 |
| 13 | 171243072000 |
| 14 | 3138418483200 |
| 15 | 61460695296000 |
| 16 | 1286751578112000 |
| 17 | 27743619391488000 |
| 18 | 640237370572800000 |
| 19 | 15448927751921664000 |
| 20 | 394130125324615680000 |
| 21 | 10422552203028725760000 |
| 22 | 288306186674956369920000 |