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 | 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 |
| 23 | -1015423886506852352 |
| 24 | 15514534163557086905 |