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 | 0 |
| 3 | 162 |
| 4 | 0 |
| 5 | -11250 |
| 6 | 0 |
| 7 | 576240 |
| 8 | 0 |
| 9 | -25259850 |
| 10 | 0 |
| 11 | 1007242236 |
| 12 | 0 |
| 13 | -37685439792 |
| 14 | 0 |
| 15 | 1346871240000 |
| 16 | 0 |
| 17 | -46504059326010 |
| 18 | 0 |
| 19 | 1562983866658500 |
| 20 | 0 |
| 21 | -51407781284599740 |
| 22 | 0 |
| 23 | 1661123953798807680 |
| 24 | 0 |
| 25 | -52886433789393750000 |
| 26 | 0 |
| 27 | 1662782404368229351200 |