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 | 2 |
| 4 | 5 |
| 5 | -16 |
| 6 | -61 |
| 7 | 272 |
| 8 | 1385 |
| 9 | -7936 |
| 10 | -50521 |
| 11 | 353792 |
| 12 | 2702765 |
| 13 | -22368256 |
| 14 | -199360981 |
| 15 | 1903757312 |
| 16 | 19391512145 |
| 17 | -209865342976 |
| 18 | -2404879675441 |
| 19 | 29088885112832 |
| 20 | 370371188237525 |
| 21 | -4951498053124096 |
| 22 | -69348874393137901 |