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 | 4580 |
| 8 | 33252 |
| 9 | 260204 |
| 10 | 2161930 |
| 11 | 18861307 |
| 12 | 171341565 |
| 13 | 1610345257 |
| 14 | 15579644765 |
| 15 | 154541844196 |
| 16 | 1566713947713 |
| 17 | 16190122718865 |
| 18 | 170171678529883 |
| 19 | 1816001425551270 |
| 20 | 19646035298044543 |
| 21 | 215179180467834605 |
| 22 | 2383465957654163227 |
| 23 | 26673704385975326866 |