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 | 2 |
| 1 | 6 |
| 2 | 30 |
| 3 | 146 |
| 4 | 698 |
| 5 | 3358 |
| 6 | 16342 |
| 7 | 80298 |
| 8 | 397170 |
| 9 | 1972790 |
| 10 | 9824654 |
| 11 | 49005250 |
| 12 | 244672042 |
| 13 | 1222297422 |
| 14 | 6108298566 |
| 15 | 30531927002 |
| 16 | 152630937314 |
| 17 | 763068593254 |
| 18 | 3815084686078 |
| 19 | 19074648589554 |
| 20 | 95370918424986 |
| 21 | 476847618556286 |