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 | -2 |
| 3 | 0 |
| 4 | 18 |
| 5 | -85 |
| 6 | 155 |
| 7 | 1057 |
| 8 | -13636 |
| 9 | 86361 |
| 10 | -271783 |
| 11 | -1518539 |
| 12 | 35743378 |
| 13 | -376883351 |
| 14 | 2663534939 |
| 15 | -8383983593 |
| 16 | -117620643336 |
| 17 | 2907896789457 |
| 18 | -39364767602331 |
| 19 | 389671721253889 |
| 20 | -2504052803057234 |
| 21 | -3842812946739679 |
| 22 | 465976686530941599 |