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 | -16 |
| 3 | 192 |
| 4 | -1904 |
| 5 | 16416 |
| 6 | -134608 |
| 7 | 1102920 |
| 8 | -8971103 |
| 9 | 69262338 |
| 10 | -527129920 |
| 11 | 4002967800 |
| 12 | -30263030000 |
| 13 | 218133853800 |
| 14 | -1565386817920 |
| 15 | 11130108480678 |
| 16 | -75244171093875 |
| 17 | 496516351214832 |
| 18 | -3261752198331472 |
| 19 | 21401161780748720 |
| 20 | -140093238345715827 |
| 21 | 914525302322457472 |