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 | 24 |
| 4 | 84 |
| 5 | 264 |
| 6 | 1128 |
| 7 | 4728 |
| 8 | 20304 |
| 9 | 86496 |
| 10 | 369732 |
| 11 | 1573608 |
| 12 | 6703068 |
| 13 | 28474704 |
| 14 | 120922272 |
| 15 | 512524704 |
| 16 | 2171836752 |
| 17 | 9190071984 |
| 18 | 38866395264 |
| 19 | 164191075824 |
| 20 | 693230730864 |