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) |
|---|---|
| 3 | 20 |
| 4 | 140 |
| 5 | 405 |
| 6 | 2856 |
| 7 | 25296 |
| 8 | 111720 |
| 9 | 25984 |
| 10 | 5474000 |
| 11 | 237600 |
| 12 | 223826688 |
| 13 | 3852800 |
| 14 | 268565760 |
| 15 | 1834725376 |
| 16 | 175861400000 |
| 17 | 335674368 |
| 18 | 2863363937280 |
| 19 | 4383831556096 |
| 20 | 206015846400 |
| 21 | 3400704000 |
| 22 | 938209120583680 |
| 23 | 2981338216980480 |
| 24 | 21463949229465600 |
| 25 | 45410367307776 |
| 26 | 72056803765911552 |