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 | 1 |
| 4 | 1 |
| 5 | 6 |
| 6 | 10 |
| 7 | 120 |
| 8 | 35 |
| 9 | 280 |
| 10 | 4536 |
| 11 | 362880 |
| 12 | 5775 |
| 13 | 39916800 |
| 14 | 24710400 |
| 15 | 8408400 |
| 16 | 2627625 |
| 17 | 1307674368000 |
| 18 | 2858856000 |
| 19 | 355687428096000 |
| 20 | 15277011750 |
| 21 | 4345461120000 |
| 22 | 4989349821456000 |
| 23 | 51090942171709440000 |
| 24 | 45092646348750 |
| 25 | 242362656927046656 |