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 | 119 |
| 6 | 694 |
| 7 | 4582 |
| 8 | 33324 |
| 9 | 261808 |
| 10 | 2190688 |
| 11 | 19318688 |
| 12 | 178108704 |
| 13 | 1705985883 |
| 14 | 16891621166 |
| 15 | 172188608886 |
| 16 | 1801013405436 |
| 17 | 19274897768196 |
| 18 | 210573149141896 |
| 19 | 2343553478425816 |
| 20 | 26525044132374656 |
| 21 | 304856947930144656 |