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 | 0 |
| 2 | -1 |
| 3 | 0 |
| 4 | 2 |
| 5 | -3 |
| 6 | -4 |
| 7 | 30 |
| 8 | -55 |
| 9 | -126 |
| 10 | 1190 |
| 11 | -3333 |
| 12 | -4522 |
| 13 | 90354 |
| 14 | -417349 |
| 15 | 290628 |
| 16 | 9897158 |
| 17 | -79200003 |
| 18 | 253387112 |
| 19 | 981776010 |
| 20 | -18675127711 |
| 21 | 120607895430 |
| 22 | -211057884214 |
| 23 | -4240412978637 |
| 24 | 54534511617962 |
| 25 | -318859368844866 |
| 26 | -1539810740197 |
| 27 | 21691972838975040 |