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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 116 |
| 6 | 672 |
| 7 | 4536 |
| 8 | 34944 |
| 9 | 302896 |
| 10 | 2916992 |
| 11 | 30899616 |
| 12 | 357080064 |
| 13 | 4470310976 |
| 14 | 60269056512 |
| 15 | 870591770496 |
| 16 | 13414154256384 |
| 17 | 219604379097856 |
| 18 | 3806644208863232 |
| 19 | 69650568655858176 |
| 20 | 1341477655028219904 |
| 21 | 27128858382696129536 |
| 22 | 574755293400886321152 |