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 | 1 |
| 3 | -2 |
| 4 | 0 |
| 5 | 288 |
| 6 | -1728 |
| 7 | -26240 |
| 8 | 222272 |
| 9 | 1636864 |
| 10 | -8434688 |
| 11 | -61820416 |
| 12 | 238704640 |
| 13 | 544024576 |
| 14 | 3294658560 |
| 15 | -71814283264 |
| 16 | 359994671104 |
| 17 | 17294535000064 |
| 18 | 302441193013248 |
| 19 | -2311203985948672 |
| 20 | -11313883306262528 |
| 21 | -31078379553816576 |
| 22 | 26574426771056230400 |