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 | 4871 |
| 8 | 37616 |
| 9 | 326376 |
| 10 | 3161321 |
| 11 | 33647702 |
| 12 | 391315387 |
| 13 | 4925158550 |
| 14 | 66783060318 |
| 15 | 969759198692 |
| 16 | 15025115932355 |
| 17 | 247300462549813 |
| 18 | 4310409307848931 |
| 19 | 79296721491391389 |
| 20 | 1535659536831254219 |
| 21 | 31225145160777718876 |
| 22 | 665165555262983848987 |