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 | 2 |
| 3 | 7 |
| 4 | 26 |
| 5 | 148 |
| 6 | 804 |
| 7 | 6228 |
| 8 | 47424 |
| 9 | 441936 |
| 10 | 4288320 |
| 11 | 50437440 |
| 12 | 560373120 |
| 13 | 7723935360 |
| 14 | 106618256640 |
| 15 | 1614841401600 |
| 16 | 25127582054400 |
| 17 | 446784010444800 |
| 18 | 7727747269939200 |
| 19 | 152873884406476800 |
| 20 | 2966599550251008000 |
| 21 | 62987912790921216000 |
| 22 | 1378192085174919168000 |