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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 118 |
| 6 | 684 |
| 7 | 4554 |
| 8 | 34192 |
| 9 | 285558 |
| 10 | 2624496 |
| 11 | 26315990 |
| 12 | 285828324 |
| 13 | 3342566724 |
| 14 | 41869664320 |
| 15 | 559265742918 |
| 16 | 7934746600620 |
| 17 | 119162454310392 |
| 18 | 1888417811354292 |
| 19 | 31492626988890798 |
| 20 | 551302582228438512 |
| 21 | 10107905106374914860 |
| 22 | 193700015975819881008 |
| 23 | 3872391687779493752340 |
| 24 | 80623321999146782133372 |