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 | 5011 |
| 8 | 39856 |
| 9 | 356616 |
| 10 | 3545280 |
| 11 | 38768400 |
| 12 | 462487631 |
| 13 | 5977005477 |
| 14 | 83186290826 |
| 15 | 1240460869290 |
| 16 | 19730730733920 |
| 17 | 333451122953921 |
| 18 | 5966845400766578 |
| 19 | 112703780178989573 |
| 20 | 2240828272067529040 |
| 21 | 46780834679854338540 |
| 22 | 1023129822229674425971 |