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 | 7 |
| 4 | 35 |
| 5 | 220 |
| 6 | 1622 |
| 7 | 13480 |
| 8 | 123212 |
| 9 | 1218694 |
| 10 | 12898292 |
| 11 | 144890911 |
| 12 | 1717072304 |
| 13 | 21367220392 |
| 14 | 278174617499 |
| 15 | 3777454890226 |
| 16 | 53372573914742 |
| 17 | 783004637781214 |
| 18 | 11905653060557285 |
| 19 | 187325244287570431 |
| 20 | 3045651218248945454 |
| 21 | 51103551998888439679 |
| 22 | 883901254149820933025 |