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 | 3 |
| 2 | 12 |
| 3 | 42 |
| 4 | 144 |
| 5 | 728 |
| 6 | 2688 |
| 7 | 10080 |
| 8 | 39312 |
| 9 | 127008 |
| 10 | 423360 |
| 11 | 2419200 |
| 12 | 6773760 |
| 13 | 32140800 |
| 14 | 160704000 |
| 15 | 626745600 |
| 16 | 1940889600 |
| 17 | 9289728000 |
| 18 | 38397542400 |
| 19 | 156332851200 |
| 20 | 642477588480 |
| 21 | 2223960883200 |
| 22 | 8154523238400 |
| 23 | 36280077926400 |