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 | 0 |
| 3 | -3 |
| 4 | 0 |
| 5 | 9 |
| 6 | 0 |
| 7 | -81 |
| 8 | 0 |
| 9 | 81 |
| 10 | 0 |
| 11 | -167913 |
| 12 | 0 |
| 13 | 2187 |
| 14 | 0 |
| 15 | -23731137 |
| 16 | 0 |
| 17 | 287811387 |
| 18 | 0 |
| 19 | -10310604939 |
| 20 | 0 |
| 21 | 13761310401 |
| 22 | 0 |
| 23 | -125613568885131 |
| 24 | 0 |
| 25 | 3146863577139 |
| 26 | 0 |
| 27 | -5409187422305481 |
| 28 | 0 |
| 29 | 8241860346410471769 |