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 | 0 |
| 2 | 2 |
| 3 | -4 |
| 4 | 8 |
| 5 | 56 |
| 6 | 28 |
| 7 | -92 |
| 8 | -1350 |
| 9 | -2446 |
| 10 | 4658 |
| 11 | -3174 |
| 12 | -101402 |
| 13 | -16318 |
| 14 | -632474 |
| 15 | -1954842 |
| 16 | 10724544 |
| 17 | 45041304 |
| 18 | 111069790 |
| 19 | 548593100 |
| 20 | 1818298480 |