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 | -7 |
| 3 | 5 |
| 4 | 193 |
| 5 | -1273 |
| 6 | -2707 |
| 7 | 118827 |
| 8 | -853551 |
| 9 | -4449558 |
| 10 | 165958491 |
| 11 | -1452523488 |
| 12 | -8908621939 |
| 13 | 425284211536 |
| 14 | -4941880813097 |
| 15 | -19601696580922 |
| 16 | 1717461768840017 |
| 17 | -27768623874128015 |
| 18 | 11072293576957975 |
| 19 | 9641864176354481835 |