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 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 480 |
| 7 | 3600 |
| 8 | 30240 |
| 9 | 151200 |
| 10 | 1693440 |
| 11 | 20321280 |
| 12 | 121927680 |
| 13 | 1828915200 |
| 14 | 28740096000 |
| 15 | 201180672000 |
| 16 | 3793692672000 |
| 17 | 73977007104000 |
| 18 | 591816056832000 |
| 19 | 13463815292928000 |
| 20 | 314155690168320000 |