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 | -1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 6 |
| 5 | -6 |
| 6 | -24 |
| 7 | -120 |
| 8 | 540 |
| 9 | 1764 |
| 10 | 2016 |
| 11 | -68256 |
| 12 | -147960 |
| 13 | 700920 |
| 14 | 11870496 |
| 15 | 5245344 |
| 16 | -330495984 |
| 17 | -2602348560 |
| 18 | 6794046720 |
| 19 | 141179998464 |
| 20 | 619736321376 |
| 21 | -6025074044256 |
| 22 | -66284988059520 |
| 23 | -87481563442560 |
| 24 | 4660723755205056 |
| 25 | 34028147176271424 |
| 26 | -98057302990861824 |