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 | 362880 |
| 11 | 3628800 |
| 12 | 19958400 |
| 13 | 159667200 |
| 14 | 1556755200 |
| 15 | 17435658240 |
| 16 | 217945728000 |
| 17 | 2988969984000 |
| 18 | 44460928512000 |
| 19 | 711374856192000 |
| 20 | 12164510040883200 |
| 21 | 221172909834240000 |
| 22 | 2322315553259520000 |
| 23 | 34060628114472960000 |