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 | 4 |
| 3 | 16 |
| 4 | 64 |
| 5 | 384 |
| 6 | 2304 |
| 7 | 18432 |
| 8 | 147456 |
| 9 | 1474560 |
| 10 | 14745600 |
| 11 | 176947200 |
| 12 | 2123366400 |
| 13 | 29727129600 |
| 14 | 416179814400 |
| 15 | 6658877030400 |
| 16 | 106542032486400 |
| 17 | 1917756584755200 |
| 18 | 34519618525593600 |
| 19 | 690392370511872000 |
| 20 | 13807847410237440000 |
| 21 | 303772643025223680000 |