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 | 4 |
| 3 | -17 |
| 4 | 87 |
| 5 | -490 |
| 6 | 2945 |
| 7 | -18517 |
| 8 | 120340 |
| 9 | -802005 |
| 10 | 5451651 |
| 11 | -37652546 |
| 12 | 263480357 |
| 13 | -1864065017 |
| 14 | 13311094644 |
| 15 | -95816113129 |
| 16 | 694511157535 |
| 17 | -5064818563258 |
| 18 | 37135165923801 |
| 19 | -273581694291309 |
| 20 | 2024194855052180 |
| 21 | -15034769479254861 |
| 22 | 112062948489702251 |
| 23 | -837936593024505298 |