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 | 6 |
| 2 | 28 |
| 3 | 132 |
| 4 | 624 |
| 5 | 2952 |
| 6 | 13968 |
| 7 | 66096 |
| 8 | 312768 |
| 9 | 1480032 |
| 10 | 7003584 |
| 11 | 33141312 |
| 12 | 156826368 |
| 13 | 742110336 |
| 14 | 3511703808 |
| 15 | 16617560832 |
| 16 | 78635142144 |
| 17 | 372105487872 |
| 18 | 1760822074368 |
| 19 | 8332299518976 |
| 20 | 39428864667648 |
| 21 | 186579390892032 |
| 22 | 882903157346304 |
| 23 | 4177942598725632 |