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 | 5 |
| 4 | -55 |
| 5 | 1045 |
| 6 | -30305 |
| 7 | 1242505 |
| 8 | -68337775 |
| 9 | 4851982025 |
| 10 | -431826400225 |
| 11 | 47069077624525 |
| 12 | -6166049168812775 |
| 13 | 955737621165980125 |
| 14 | -172988509431042402625 |
| 15 | 36154598471087862148625 |
| 16 | -8640949034589999053521375 |
| 17 | 2341697188373889743504292625 |