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 | 1 |
| 2 | 6 |
| 3 | 30 |
| 4 | 144 |
| 5 | 687 |
| 6 | 3296 |
| 7 | 15972 |
| 8 | 78294 |
| 9 | 388320 |
| 10 | 1947910 |
| 11 | 9875566 |
| 12 | 50560246 |
| 13 | 261177401 |
| 14 | 1360112590 |
| 15 | 7134802722 |
| 16 | 37673830960 |
| 17 | 200106632766 |
| 18 | 1068539351340 |
| 19 | 5733226876876 |
| 20 | 30894846668416 |
| 21 | 167137498306038 |
| 22 | 907416216735816 |