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 | 2 |
| 2 | 4 |
| 3 | 24 |
| 4 | 208 |
| 5 | 2272 |
| 6 | 29504 |
| 7 | 441216 |
| 8 | 7447808 |
| 9 | 139951616 |
| 10 | 2897228800 |
| 11 | 65533753344 |
| 12 | 1608679247872 |
| 13 | 42607095439360 |
| 14 | 1211489065582592 |
| 15 | 36818002833014784 |
| 16 | 1191230067009978368 |
| 17 | 40888060455008731136 |
| 18 | 1484180363633916903424 |
| 19 | 56809679459301490950144 |
| 20 | 2287045885619374501396480 |
| 21 | 96608773951155028111654912 |