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 | -2 |
| 3 | 8 |
| 4 | -34 |
| 5 | 158 |
| 6 | -768 |
| 7 | 3858 |
| 8 | -19851 |
| 9 | 104023 |
| 10 | -552974 |
| 11 | 2973832 |
| 12 | -16146688 |
| 13 | 88376636 |
| 14 | -487034106 |
| 15 | 2699839758 |
| 16 | -15043262970 |
| 17 | 84197804254 |
| 18 | -473140314356 |
| 19 | 2668221663736 |
| 20 | -15095165871964 |
| 21 | 85645090974518 |
| 22 | -487190919969502 |