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 | 2 |
| 3 | -4 |
| 4 | 17 |
| 5 | -92 |
| 6 | 576 |
| 7 | -4156 |
| 8 | 34159 |
| 9 | -314368 |
| 10 | 3199936 |
| 11 | -35703996 |
| 12 | 433421495 |
| 13 | -5687955724 |
| 14 | 80256879068 |
| 15 | -1211781887796 |
| 16 | 19496946534720 |
| 17 | -333041104402860 |
| 18 | 6019770247224496 |
| 19 | -114794574818830716 |
| 20 | 2303332661416242633 |
| 21 | -48509766592884311132 |
| 22 | 1069983257387168051076 |