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 | 0 |
| 4 | -1 |
| 5 | -10 |
| 6 | -65 |
| 7 | -350 |
| 8 | -1631 |
| 9 | -5250 |
| 10 | 18395 |
| 11 | 685850 |
| 12 | 10485739 |
| 13 | 127737610 |
| 14 | 1336804105 |
| 15 | 11432407350 |
| 16 | 54280609109 |
| 17 | -712071643930 |
| 18 | -29671691715185 |
| 19 | -660215774400350 |
| 20 | -11770593620859521 |
| 21 | -176475952496559870 |
| 22 | -2055362595355830475 |
| 23 | -9749893741512339250 |