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 | 1 |
| 3 | 9 |
| 4 | 59 |
| 5 | 450 |
| 6 | 4114 |
| 7 | 43512 |
| 8 | 528492 |
| 9 | 7235568 |
| 10 | 110499696 |
| 11 | 1862118720 |
| 12 | 34342356960 |
| 13 | 688092312960 |
| 14 | 14886351037440 |
| 15 | 345878769358080 |
| 16 | 8590707803462400 |
| 17 | 227153424885811200 |
| 18 | 6371121297516595200 |