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 | 4885 |
| 8 | 37840 |
| 9 | 329400 |
| 10 | 3182400 |
| 11 | 33778800 |
| 12 | 391590750 |
| 13 | 4915323791 |
| 14 | 66442003448 |
| 15 | 962278914330 |
| 16 | 14866633343040 |
| 17 | 244014015391725 |
| 18 | 4240899164064012 |
| 19 | 77799960323395327 |
| 20 | 1502369690026049320 |
| 21 | 30462229695574890900 |
| 22 | 647071778569768101485 |