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 | -4 |
| 3 | -21 |
| 4 | -160 |
| 5 | -1505 |
| 6 | -17136 |
| 7 | -226093 |
| 8 | -3334528 |
| 9 | -53031105 |
| 10 | -864640000 |
| 11 | -12957006821 |
| 12 | -107329453056 |
| 13 | 4548002439071 |
| 14 | 409321789829120 |
| 15 | 23780752998703875 |
| 16 | 1257249577352658944 |
| 17 | 65336038911885770623 |