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) |
|---|---|
| 1 | -1 |
| 2 | 1 |
| 3 | -4 |
| 4 | 18 |
| 5 | -92 |
| 6 | 572 |
| 7 | -4156 |
| 8 | 34177 |
| 9 | -314368 |
| 10 | 3199844 |
| 11 | -35703996 |
| 12 | 433422067 |
| 13 | -5687955724 |
| 14 | 80256874912 |
| 15 | -1211781887796 |
| 16 | 19496946568897 |
| 17 | -333041104402860 |
| 18 | 6019770246910128 |
| 19 | -114794574818830716 |
| 20 | 2303332661419442477 |
| 21 | -48509766592884311132 |
| 22 | 1069983257387132347080 |