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) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 28 |
| 4 | 190 |
| 5 | 1692 |
| 6 | 16766 |
| 7 | 166028 |
| 8 | 1586430 |
| 9 | 14580412 |
| 10 | 129654526 |
| 11 | 1123451628 |
| 12 | 9544185470 |
| 13 | 79881877532 |
| 14 | 661135445886 |
| 15 | 5425962250828 |
| 16 | 44250287565310 |
| 17 | 359161631645052 |
| 18 | 2904756409742846 |
| 19 | 23429320590259628 |
| 20 | 188594431902253950 |