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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 24 |
| 5 | 160 |
| 6 | 1290 |
| 7 | 11046 |
| 8 | 106848 |
| 9 | 1117152 |
| 10 | 12849840 |
| 11 | 159089040 |
| 12 | 2132602560 |
| 13 | 30554297280 |
| 14 | 468754715520 |
| 15 | 7634862748800 |
| 16 | 132058767052800 |
| 17 | 2410986506342400 |
| 18 | 46443330717235200 |
| 19 | 939668036761036800 |
| 20 | 19955747250238464000 |
| 21 | 443271664862659584000 |
| 22 | 10290986066890045440000 |