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 | -2 |
| 3 | 10 |
| 4 | 24 |
| 5 | -312 |
| 6 | -560 |
| 7 | 19472 |
| 8 | 6272 |
| 9 | -1994624 |
| 10 | 4072704 |
| 11 | 299059968 |
| 12 | -1635814400 |
| 13 | -60723321856 |
| 14 | 628215191552 |
| 15 | 15716076562432 |
| 16 | -274420622327808 |
| 17 | -4900668238036992 |
| 18 | 140182198527655936 |
| 19 | 1717697481518809088 |
| 20 | -83651335147070685184 |
| 21 | -590374211868638314496 |