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 | -2 |
| 4 | 9 |
| 5 | -44 |
| 6 | 175 |
| 7 | 246 |
| 8 | -21007 |
| 9 | 396712 |
| 10 | -5576769 |
| 11 | 57840850 |
| 12 | -151112951 |
| 13 | -14137899060 |
| 14 | 539212013327 |
| 15 | -13335393617714 |
| 16 | 239914650459105 |
| 17 | -1990873438067504 |
| 18 | -76974185162417921 |
| 19 | 5220283004540970282 |
| 20 | -194958036625254566599 |
| 21 | 5226632355735840377140 |