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 | 0 |
| 3 | 8 |
| 4 | 78 |
| 5 | 764 |
| 6 | 8310 |
| 7 | 100988 |
| 8 | 1362438 |
| 9 | 20246444 |
| 10 | 328972470 |
| 11 | 5805917468 |
| 12 | 110645911398 |
| 13 | 2265191981324 |
| 14 | 49589790516630 |
| 15 | 1156201277261948 |
| 16 | 28605950745797958 |
| 17 | 748605590542359404 |
| 18 | 20661245832389468790 |
| 19 | 599820758571599742428 |
| 20 | 18272940402442730318118 |