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 | 20 |
| 2 | 210 |
| 3 | 1540 |
| 4 | 8855 |
| 5 | 42504 |
| 6 | 177100 |
| 7 | 657800 |
| 8 | 2220075 |
| 9 | 6906900 |
| 10 | 20030010 |
| 11 | 54627084 |
| 12 | 141116637 |
| 13 | 347336412 |
| 14 | 818558424 |
| 15 | 1854631380 |
| 16 | 4053948342 |
| 17 | 8574134256 |
| 18 | 17590903116 |
| 19 | 35084425512 |
| 20 | 68153183370 |
| 21 | 129156542039 |