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 | -2 |
| 2 | 8 |
| 3 | -24 |
| 4 | 84 |
| 5 | -272 |
| 6 | 920 |
| 7 | -3040 |
| 8 | 10180 |
| 9 | -33840 |
| 10 | 112968 |
| 11 | -376224 |
| 12 | 1254696 |
| 13 | -4181088 |
| 14 | 13939248 |
| 15 | -46459584 |
| 16 | 154873860 |
| 17 | -516229040 |
| 18 | 1720795880 |
| 19 | -5735921440 |
| 20 | 19119861304 |
| 21 | -63732624672 |
| 22 | 212442552528 |
| 23 | -708140901184 |
| 24 | 2360471473384 |
| 25 | -7868234639072 |