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 | -7 |
| 3 | 49 |
| 4 | -427 |
| 5 | 4165 |
| 6 | -43435 |
| 7 | 473977 |
| 8 | -5344333 |
| 9 | 61772179 |
| 10 | -727993301 |
| 11 | 8714701219 |
| 12 | -105672771225 |
| 13 | 1295237037815 |
| 14 | -16021641194545 |
| 15 | 199747074505773 |
| 16 | -2507395464414008 |
| 17 | 31664298046926328 |
| 18 | -401994771266030880 |
| 19 | 5127701624204157600 |
| 20 | -65684716411944207144 |