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 | 0 |
| 2 | 1 |
| 3 | 9 |
| 4 | 119 |
| 5 | 2025 |
| 6 | 42510 |
| 7 | 1062761 |
| 8 | 30854159 |
| 9 | 1020615912 |
| 10 | 37900765365 |
| 11 | 1561459425955 |
| 12 | 70682817696436 |
| 13 | 3487456195458027 |
| 14 | 186281997929231659 |
| 15 | 10709829446929099865 |
| 16 | 659427284782849503663 |
| 17 | 43293574636994934145044 |
| 18 | 3019108475859713906967738 |
| 19 | 222868205832269470083471366 |