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 | 0 |
| 1 | 0 |
| 2 | 72 |
| 3 | 1296 |
| 4 | 15552 |
| 5 | 155520 |
| 6 | 1399680 |
| 7 | 11757312 |
| 8 | 94058496 |
| 9 | 725594112 |
| 10 | 5441955840 |
| 11 | 39907676160 |
| 12 | 287335268352 |
| 13 | 2037468266496 |
| 14 | 14262277865472 |
| 15 | 98738846760960 |
| 16 | 677066377789440 |
| 17 | 4604051368968192 |
| 18 | 31077346740535296 |
| 19 | 208401031083589632 |
| 20 | 1389340207223930880 |
| 21 | 9213519268958699520 |