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 | 4 |
| 2 | 12 |
| 3 | 132 |
| 4 | 3156 |
| 5 | 136980 |
| 6 | 10015092 |
| 7 | 1199364852 |
| 8 | 234207001236 |
| 9 | 75018740661780 |
| 10 | 39745330657406772 |
| 11 | 35073541377640231092 |
| 12 | 51798833078501480220756 |
| 13 | 128412490016744675540378580 |
| 14 | 535348496386845235339961362932 |
| 15 | 3757366291145650829115977555259252 |