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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | -3 |
| 5 | 3 |
| 6 | 17 |
| 7 | -17 |
| 8 | -155 |
| 9 | 155 |
| 10 | 2073 |
| 11 | -2073 |
| 12 | -38227 |
| 13 | 38227 |
| 14 | 929569 |
| 15 | -929569 |
| 16 | -28820619 |
| 17 | 28820619 |
| 18 | 1109652905 |
| 19 | -1109652905 |
| 20 | -51943281731 |
| 21 | 51943281731 |
| 22 | 2905151042481 |
| 23 | -2905151042481 |
| 24 | -191329672483963 |
| 25 | 191329672483963 |
| 26 | 14655626154768697 |
| 27 | -14655626154768697 |