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 | 0 |
| 4 | -3 |
| 5 | -8 |
| 6 | -3 |
| 7 | 56 |
| 8 | 217 |
| 9 | 64 |
| 10 | -2951 |
| 11 | -12672 |
| 12 | 5973 |
| 13 | 309376 |
| 14 | 1237173 |
| 15 | -2917888 |
| 16 | -52635599 |
| 17 | -163782656 |
| 18 | 1126610929 |
| 19 | 12716052480 |
| 20 | 20058390573 |
| 21 | -495644917760 |
| 22 | -3920482183827 |
| 23 | 4004259037184 |
| 24 | 256734635981833 |
| 25 | 1359174582304768 |