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 | 7 |
| 4 | -63 |
| 5 | 801 |
| 6 | -13025 |
| 7 | 258343 |
| 8 | -6048511 |
| 9 | 163276417 |
| 10 | -4992740289 |
| 11 | 170571634311 |
| 12 | -6439161507647 |
| 13 | 266180947507489 |
| 14 | -11958385377911713 |
| 15 | 580151397382158631 |
| 16 | -30227616424300542975 |
| 17 | 1683438461080186841601 |
| 18 | -99796591057813372007297 |