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 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 30 |
| 5 | 109 |
| 6 | 420 |
| 7 | 1685 |
| 8 | 6960 |
| 9 | 29391 |
| 10 | 126291 |
| 11 | 550359 |
| 12 | 2426502 |
| 13 | 10803801 |
| 14 | 48507843 |
| 15 | 219377949 |
| 16 | 998436792 |
| 17 | 4569488371 |
| 18 | 21016589073 |
| 19 | 97090411019 |
| 20 | 450314942682 |
| 21 | 2096122733211 |
| 22 | 9788916220518 |
| 23 | 45850711498859 |
| 24 | 215348942668680 |
| 25 | 1013979873542689 |
| 26 | 4785437476592805 |
| 27 | 22633143884165985 |
| 28 | 107258646298581390 |