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 | 2 |
| 4 | 6 |
| 5 | 24 |
| 6 | 120 |
| 7 | 720 |
| 8 | 5040 |
| 9 | 40320 |
| 10 | 359520 |
| 11 | 3590400 |
| 12 | 39362400 |
| 13 | 472919040 |
| 14 | 6133670400 |
| 15 | 85948262400 |
| 16 | 1284106824000 |
| 17 | 20434058444800 |
| 18 | 345796766515200 |
| 19 | 6188467544064000 |
| 20 | 117398964114432000 |
| 21 | 2341018467532800000 |
| 22 | 49035684501872640000 |
| 23 | 1074839883779211264000 |