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 | -13 |
| 3 | 21 |
| 4 | 323 |
| 5 | -1141 |
| 6 | -157531 |
| 7 | 123361 |
| 8 | 3107843 |
| 9 | -22584681 |
| 10 | -7737133583 |
| 11 | 6298701101 |
| 12 | 21361359585233 |
| 13 | -2489518886621 |
| 14 | -108166545951373 |
| 15 | 1324340625653241 |
| 16 | 1117741969306140211 |
| 17 | -912462507809610961 |
| 18 | -6777866017304661816769 |
| 19 | 790465529030548467781 |