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 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 24 |
| 6 | 180 |
| 7 | 720 |
| 8 | 840 |
| 9 | 20160 |
| 10 | 378000 |
| 11 | 3628800 |
| 12 | 6985440 |
| 13 | 479001600 |
| 14 | 6235669440 |
| 15 | 47221574400 |
| 16 | 259459200 |
| 17 | 20922789888000 |
| 18 | 2972883513600 |
| 19 | 6402373705728000 |
| 20 | 20274518622758400 |
| 21 | 1219830034655232000 |
| 22 | 51090956251003468800 |
| 23 | 1124000727777607680000 |