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 | 1 |
| 3 | 6 |
| 4 | 28 |
| 5 | 235 |
| 6 | 2466 |
| 7 | 31864 |
| 8 | 488328 |
| 9 | 8901981 |
| 10 | 183417490 |
| 11 | 4300791946 |
| 12 | 111621409956 |
| 13 | 3214239089659 |
| 14 | 100662133475372 |
| 15 | 3440691046061130 |
| 16 | 126342964714732576 |
| 17 | 4999000389915029881 |
| 18 | 210671936366279249610 |
| 19 | 9474491260037610708598 |
| 20 | 450638933972015166026220 |