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 | 0 |
| 3 | 1 |
| 4 | -5 |
| 5 | 9 |
| 6 | -329 |
| 7 | 3655 |
| 8 | -11961 |
| 9 | 721315 |
| 10 | -12310199 |
| 11 | 29326887 |
| 12 | -4939227215 |
| 13 | 113836841041 |
| 14 | -356357531655 |
| 15 | 77087063678521 |
| 16 | -2238375706930349 |
| 17 | 17366683494629835 |
| 18 | -2294640596998068569 |
| 19 | 80381887628910919255 |