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 | 4 |
| 3 | 220 |
| 4 | 60092152 |
| 5 | 203720181459953921762400 |
| 6 | 7088043372247785801830314829178419617696182324188730917543544992 |