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 | 720 |
| 7 | 720 |
| 8 | 5760 |
| 9 | 51840 |
| 10 | 518400 |
| 11 | 5702400 |
| 12 | 68428800 |
| 13 | 889574400 |
| 14 | 889574400 |
| 15 | 13343616000 |
| 16 | 213497856000 |
| 17 | 3629463552000 |
| 18 | 65330343936000 |
| 19 | 1241276534784000 |
| 20 | 24825530695680000 |
| 21 | 24825530695680000 |
| 22 | 546161675304960000 |
| 23 | 12561718532014080000 |
| 24 | 301481244768337920000 |
| 25 | 7537031119208448000000 |