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 | 5 |
| 4 | 20 |
| 5 | 95 |
| 6 | 560 |
| 7 | 3858 |
| 8 | 30478 |
| 9 | 271253 |
| 10 | 2685396 |
| 11 | 29270807 |
| 12 | 348322597 |
| 13 | 4493361501 |
| 14 | 62457724854 |
| 15 | 930620100319 |
| 16 | 14796859595059 |
| 17 | 250066927156482 |
| 18 | 4476197996101024 |
| 19 | 84600142126309336 |
| 20 | 1683542828313555775 |