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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 24 |
| 6 | 140 |
| 7 | 792 |
| 8 | 4752 |
| 9 | 27072 |
| 10 | 230832 |
| 11 | 1991952 |
| 12 | 17927568 |
| 13 | 155644416 |
| 14 | 1780206336 |
| 15 | 20695108608 |
| 16 | 248341303296 |
| 17 | 2898196070400 |
| 18 | 41713375334400 |
| 19 | 610011772416000 |
| 20 | 9150176586240000 |
| 21 | 134163172454400000 |
| 22 | 2329812142295040000 |