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 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 12 |
| 5 | 48 |
| 6 | 192 |
| 7 | 960 |
| 8 | 5760 |
| 9 | 34560 |
| 10 | 241920 |
| 11 | 1935360 |
| 12 | 15482880 |
| 13 | 139345920 |
| 14 | 1393459200 |
| 15 | 13934592000 |
| 16 | 153280512000 |
| 17 | 1839366144000 |
| 18 | 22072393728000 |
| 19 | 286941118464000 |
| 20 | 4017175658496000 |
| 21 | 56240459218944000 |