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 | 2 |
| 2 | 12 |
| 3 | 36 |
| 4 | 312 |
| 5 | 1040 |
| 6 | 7200 |
| 7 | 25088 |
| 8 | 183808 |
| 9 | 557928 |
| 10 | 4396800 |
| 11 | 15333120 |
| 12 | 121680000 |
| 13 | 406812744 |
| 14 | 2817007200 |
| 15 | 8558784000 |
| 16 | 76264519680 |
| 17 | 254230063200 |
| 18 | 1710194342400 |
| 19 | 6349120596480 |
| 20 | 47334145996800 |
| 21 | 127169887444992 |
| 22 | 1088029470747648 |
| 23 | 3889097389599864 |