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 | -10 |
| 2 | 60 |
| 3 | -280 |
| 4 | 1110 |
| 5 | -3912 |
| 6 | 12600 |
| 7 | -37760 |
| 8 | 106620 |
| 9 | -286290 |
| 10 | 736184 |
| 11 | -1822920 |
| 12 | 4365800 |
| 13 | -10149320 |
| 14 | 22971120 |
| 15 | -50744448 |
| 16 | 109643350 |
| 17 | -232145040 |
| 18 | 482403060 |
| 19 | -985229640 |
| 20 | 1980034104 |
| 21 | -3920000400 |
| 22 | 7652388280 |
| 23 | -14742829440 |