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) |
|---|---|
| 4 | 2 |
| 5 | 15 |
| 6 | 75 |
| 7 | 308 |
| 8 | 1120 |
| 9 | 3744 |
| 10 | 11760 |
| 11 | 35200 |
| 12 | 101376 |
| 13 | 282880 |
| 14 | 768768 |
| 15 | 2042880 |
| 16 | 5324800 |
| 17 | 13647872 |
| 18 | 34467840 |
| 19 | 85917696 |
| 20 | 211681280 |
| 21 | 516096000 |
| 22 | 1246429184 |
| 23 | 2984509440 |
| 24 | 7090470912 |
| 25 | 16724787200 |
| 26 | 39190528000 |
| 27 | 91276443648 |
| 28 | 211392921600 |
| 29 | 487025803264 |
| 30 | 1116607610880 |