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) |
|---|---|
| 2 | 1 |
| 3 | 12 |
| 4 | 120 |
| 5 | 1140 |
| 6 | 10626 |
| 7 | 98280 |
| 8 | 906192 |
| 9 | 8347680 |
| 10 | 76904685 |
| 11 | 708930508 |
| 12 | 6540715896 |
| 13 | 60403728840 |
| 14 | 558383307300 |
| 15 | 5166863427600 |
| 16 | 47855699958816 |
| 17 | 443643407165376 |
| 18 | 4116305022165108 |
| 19 | 38223742100828400 |
| 20 | 355214207837288800 |