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 | -47 |
| 5 | -239 |
| 6 | 121 |
| 7 | 19321 |
| 8 | 261409 |
| 9 | 1449505 |
| 10 | -20428559 |
| 11 | -730564559 |
| 12 | -10403326559 |
| 13 | -10910781023 |
| 14 | 3713153976169 |
| 15 | 108037345645321 |
| 16 | 1301173754543041 |
| 17 | -22441761904964159 |
| 18 | -1628466860540690207 |
| 19 | -41339196023230498463 |
| 20 | -189173461196772118079 |