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) |
|---|---|
| 6 | 1 |
| 7 | 0 |
| 8 | 15 |
| 9 | 70 |
| 10 | 432 |
| 11 | 4320 |
| 12 | 30855 |
| 13 | 294840 |
| 14 | 2883240 |
| 15 | 28175952 |
| 16 | 310690800 |
| 17 | 3458941920 |
| 18 | 40459730640 |
| 19 | 499638948480 |
| 20 | 6324655705200 |
| 21 | 83653192972800 |
| 22 | 1145266802114400 |
| 23 | 16145338385736000 |
| 24 | 235579813593453000 |
| 25 | 3535776409508703360 |
| 26 | 54571687068401395200 |
| 27 | 866268656574795936000 |