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 | 96 |
| 6 | 456 |
| 7 | 2472 |
| 8 | 14736 |
| 9 | 92304 |
| 10 | 632736 |
| 11 | 4661856 |
| 12 | 36364032 |
| 13 | 297668736 |
| 14 | 2583425664 |
| 15 | 23550535296 |
| 16 | 224086162176 |
| 17 | 2221083839232 |
| 18 | 22976670905856 |
| 19 | 246829966447104 |
| 20 | 2745834333566976 |
| 21 | 31605782067081216 |
| 22 | 376290722808502272 |