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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | 4 |
| 5 | -24 |
| 6 | 179 |
| 7 | -1542 |
| 8 | 14779 |
| 9 | -154147 |
| 10 | 1724785 |
| 11 | -20499916 |
| 12 | 256971448 |
| 13 | -3379187370 |
| 14 | 46424470573 |
| 15 | -664168673391 |
| 16 | 9868894159044 |
| 17 | -151977742507208 |
| 18 | 2421172940293208 |
| 19 | -39841228681799385 |
| 20 | 676261674504977841 |
| 21 | -11826431722547287115 |
| 22 | 212855326803518472588 |
| 23 | -3938986085164523720874 |