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 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 1 |
| 7 | 1 |
| 8 | 1 |
| 9 | 22680 |
| 10 | 1 |
| 11 | 1 |
| 12 | 5040 |
| 13 | 3742560 |
| 14 | 4540536000 |
| 15 | 1 |
| 16 | 1 |
| 17 | 113400 |
| 18 | 851370480 |
| 19 | 6518191680000 |
| 20 | 54111175679736000 |