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 | -1 |
| 3 | -5 |
| 4 | -35 |
| 5 | -319 |
| 6 | -3557 |
| 7 | -46617 |
| 8 | -699547 |
| 9 | -11801263 |
| 10 | -220778973 |
| 11 | -4532376577 |
| 12 | -101246459811 |
| 13 | -2444155497191 |
| 14 | -63397685488165 |
| 15 | -1758278168174137 |
| 16 | -51920205021872395 |
| 17 | -1626358286062507551 |
| 18 | -53865503179448478605 |
| 19 | -1880864793407486366353 |