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 | 2 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 72 |
| 5 | 480 |
| 6 | 4320 |
| 7 | 45360 |
| 8 | 564480 |
| 9 | 7983360 |
| 10 | 127008000 |
| 11 | 2235340800 |
| 12 | 43110144000 |
| 13 | 902918016000 |
| 14 | 20399720140800 |
| 15 | 494300911104000 |
| 16 | 12783824621568000 |
| 17 | 351419178958848000 |
| 18 | 10230993181753344000 |