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 | -3 |
| 3 | 8 |
| 4 | -28 |
| 5 | 119 |
| 6 | -581 |
| 7 | 3345 |
| 8 | -22352 |
| 9 | 170889 |
| 10 | -1480881 |
| 11 | 14361885 |
| 12 | -154177068 |
| 13 | 1814792589 |
| 14 | -23230500541 |
| 15 | 321160966833 |
| 16 | -4767464107904 |
| 17 | 75612375796689 |
| 18 | -1275789176648193 |
| 19 | 22815192314465685 |
| 20 | -431023517858496044 |