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) |
|---|---|
| 1 | 0 |
| 2 | 21 |
| 3 | 252 |
| 4 | 147420 |
| 5 | 213402 |
| 6 | 1711962 |
| 7 | 16092433 |
| 8 | 76545756 |
| 9 | 1068263553 |
| 10 | 39258683100 |
| 11 | 57497839826 |
| 12 | 58573445322 |
| 13 | 68675650561 |
| 14 | 3680015145170 |
| 15 | 3749808363210 |
| 16 | 4238480197777 |
| 17 | 4397695901697 |
| 18 | 20104741893852 |