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 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | -8 |
| 5 | -84 |
| 6 | -504 |
| 7 | -2304 |
| 8 | -6656 |
| 9 | 15760 |
| 10 | 484000 |
| 11 | 5348320 |
| 12 | 44393856 |
| 13 | 288642368 |
| 14 | 1137006976 |
| 15 | -5372233216 |
| 16 | -195241910272 |
| 17 | -2961479980800 |
| 18 | -34259767672320 |
| 19 | -320473550808576 |
| 20 | -2158264400250880 |
| 21 | -1727938748171264 |
| 22 | 278774033845987328 |