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 | 6 |
| 5 | 26 |
| 6 | 108 |
| 7 | 492 |
| 8 | 2562 |
| 9 | 14790 |
| 10 | 98874 |
| 11 | 720614 |
| 12 | 5908394 |
| 13 | 52572682 |
| 14 | 516141316 |
| 15 | 5422012074 |
| 16 | 61889630476 |
| 17 | 749456000504 |
| 18 | 9767057565198 |
| 19 | 134007980469502 |
| 20 | 1958535740848524 |