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 | 9 |
| 4 | -68 |
| 5 | 740 |
| 6 | -10554 |
| 7 | 185906 |
| 8 | -3891320 |
| 9 | 94259952 |
| 10 | -2592071760 |
| 11 | 79748398752 |
| 12 | -2713685928744 |
| 13 | 101184283477680 |
| 14 | -4102325527316184 |
| 15 | 179674073609647080 |
| 16 | -8454031849605513024 |
| 17 | 425281651659459346944 |
| 18 | -22777115050468598701248 |