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 | 7 |
| 4 | -16 |
| 5 | 40 |
| 6 | -117 |
| 7 | 411 |
| 8 | -1720 |
| 9 | 8384 |
| 10 | -46561 |
| 11 | 289595 |
| 12 | -1991504 |
| 13 | 14993108 |
| 14 | -122595085 |
| 15 | 1081616659 |
| 16 | -10239597968 |
| 17 | 103522029312 |
| 18 | -1113074512289 |
| 19 | 12681693805203 |
| 20 | -152613117638712 |
| 21 | 1934275341388596 |
| 22 | -25753344727083773 |