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) |
|---|---|
| 4 | 1 |
| 5 | 20 |
| 6 | 300 |
| 7 | 4200 |
| 8 | 58800 |
| 9 | 846720 |
| 10 | 12700800 |
| 11 | 199584000 |
| 12 | 3293136000 |
| 13 | 57081024000 |
| 14 | 1038874636800 |
| 15 | 19833061248000 |
| 16 | 396661224960000 |
| 17 | 8299373322240000 |
| 18 | 181400588328960000 |
| 19 | 4135933413900288000 |
| 20 | 98228418580131840000 |
| 21 | 2426819753156198400000 |
| 22 | 62288373664342425600000 |