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 | 1 |
| 2 | 4 |
| 3 | 25 |
| 4 | 190 |
| 5 | 1606 |
| 6 | 14506 |
| 7 | 137089 |
| 8 | 1338790 |
| 9 | 13403950 |
| 10 | 136846144 |
| 11 | 1419257434 |
| 12 | 14911016596 |
| 13 | 158363649640 |
| 14 | 1697452010230 |
| 15 | 18338919413425 |
| 16 | 199496184219910 |
| 17 | 2183299541440150 |
| 18 | 24021874198331080 |
| 19 | 265559590979820910 |
| 20 | 2948253066186839140 |
| 21 | 32857382497018933060 |