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 | 3 |
| 4 | 20 |
| 5 | 180 |
| 6 | 2058 |
| 7 | 28672 |
| 8 | 472392 |
| 9 | 9000000 |
| 10 | 194871710 |
| 11 | 4729798656 |
| 12 | 127253992476 |
| 13 | 3760310514688 |
| 14 | 121096582031250 |
| 15 | 4222124650659840 |
| 16 | 158473248526494992 |
| 17 | 6371827248895377408 |
| 18 | 273260286537746369382 |
| 19 | 12451840000000000000000 |