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 | 3 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 2 |
| 7 | 3 |
| 8 | 9 |
| 9 | 27 |
| 10 | 81 |
| 11 | 729 |
| 12 | 0 |
| 13 | 59049 |
| 14 | -531441 |
| 15 | 14348907 |
| 16 | -387420489 |
| 17 | 10460353203 |
| 18 | -564859072962 |
| 19 | 22876792454961 |
| 20 | -1853020188851841 |
| 21 | 150094635296999121 |
| 22 | -12157665459056928801 |
| 23 | 2954312706550833698643 |
| 24 | 0 |