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 | 2 |
| 4 | 5 |
| 5 | 2 |
| 6 | 18 |
| 7 | -19 |
| 8 | 115 |
| 9 | -296 |
| 10 | 1115 |
| 11 | -3632 |
| 12 | 12868 |
| 13 | -44803 |
| 14 | 159577 |
| 15 | -570455 |
| 16 | 2059182 |
| 17 | -7476086 |
| 18 | 27311129 |
| 19 | -100274479 |
| 20 | 369888135 |
| 21 | -1370063926 |
| 22 | 5093782015 |
| 23 | -19002596870 |
| 24 | 71109902844 |
| 25 | -266855928791 |
| 26 | 1004045621663 |
| 27 | -3786790876945 |