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 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | -24 |
| 5 | 60 |
| 6 | 240 |
| 7 | -4830 |
| 8 | 39984 |
| 9 | -180936 |
| 10 | -605520 |
| 11 | 24616350 |
| 12 | -318005160 |
| 13 | 2385790836 |
| 14 | -86488584 |
| 15 | -350543790870 |
| 16 | 6917020827360 |
| 17 | -79778558317200 |
| 18 | 357117438258144 |
| 19 | 9237998478286134 |
| 20 | -304182278908538040 |
| 21 | 5166739059890655660 |
| 22 | -48968796671246843160 |