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 | -21 |
| 2 | 210 |
| 3 | -1351 |
| 4 | 6426 |
| 5 | -24780 |
| 6 | 82845 |
| 7 | -250806 |
| 8 | 703731 |
| 9 | -1853481 |
| 10 | 4628337 |
| 11 | -11052867 |
| 12 | 25403952 |
| 13 | -56451192 |
| 14 | 121738767 |
| 15 | -255623851 |
| 16 | 524037507 |
| 17 | -1051143723 |
| 18 | 2066899387 |
| 19 | -3990768663 |
| 20 | 7577013360 |
| 21 | -14163858895 |