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 | 20 |
| 2 | 508 |
| 3 | 17400 |
| 4 | 788688 |
| 5 | 46032768 |
| 6 | 3372731136 |
| 7 | 303444195840 |
| 8 | 32898989030400 |
| 9 | 4229445205094400 |
| 10 | 635789661109862400 |
| 11 | 110396039984094412800 |
| 12 | 21901378996153294848000 |
| 13 | 4915686113045739601920000 |