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 | 5 |
| 3 | -17 |
| 4 | 77 |
| 5 | -345 |
| 6 | 1653 |
| 7 | -8097 |
| 8 | 40733 |
| 9 | -208553 |
| 10 | 1084421 |
| 11 | -5708785 |
| 12 | 30370861 |
| 13 | -163019641 |
| 14 | 881790357 |
| 15 | -4801746753 |
| 16 | 26302052925 |
| 17 | -144825094473 |
| 18 | 801155664933 |
| 19 | -4450426297233 |
| 20 | 24815385947469 |
| 21 | -138842668857369 |
| 22 | 779247587235765 |
| 23 | -4385948395419873 |
| 24 | 24750623835149661 |