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 | -24 |
| 2 | 252 |
| 3 | -1520 |
| 4 | 5982 |
| 5 | -18240 |
| 6 | 57320 |
| 7 | -198192 |
| 8 | 604389 |
| 9 | -1567840 |
| 10 | 4210116 |
| 11 | -12229632 |
| 12 | 32349958 |
| 13 | -77844000 |
| 14 | 196563240 |
| 15 | -510760752 |
| 16 | 1233110610 |
| 17 | -2871650184 |
| 18 | 6899741020 |
| 19 | -16499031456 |
| 20 | 37934952672 |
| 21 | -86122235648 |