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 | 6 |
| 4 | 33 |
| 5 | 4200 |
| 6 | 4192200 |
| 7 | 1705200 |
| 8 | 77892963984 |
| 9 | 10086416728304192640 |
| 10 | 126556188275836361347200 |
| 11 | 451535899566923284351392000 |
| 12 | 1253032399528279799996000622278320876800 |