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 | -5 |
| 4 | 13 |
| 5 | 101 |
| 6 | -389 |
| 7 | -4241 |
| 8 | 21785 |
| 9 | 305353 |
| 10 | -1960649 |
| 11 | -33588829 |
| 12 | 258805669 |
| 13 | 5239857325 |
| 14 | -47102631757 |
| 15 | -1100370038249 |
| 16 | 11304631621681 |
| 17 | 299300650403729 |
| 18 | -3459217276234385 |
| 19 | -102360822438075317 |
| 20 | 1314502564969066301 |
| 21 | 42991545423991633141 |
| 22 | -607300185015708631061 |