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 | 0 |
| 3 | 2 |
| 4 | 20 |
| 5 | 256 |
| 6 | 2086 |
| 7 | 16376 |
| 8 | 121418 |
| 9 | 871258 |
| 10 | 6077730 |
| 11 | 41586532 |
| 12 | 280783434 |
| 13 | 1875742356 |
| 14 | 12432917916 |
| 15 | 81868580330 |
| 16 | 536476588416 |
| 17 | 3501125753910 |
| 18 | 22778101455784 |