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 | 6 |
| 3 | 38 |
| 4 | 276 |
| 5 | 2276 |
| 6 | 21032 |
| 7 | 215336 |
| 8 | 2419824 |
| 9 | 29611120 |
| 10 | 391950240 |
| 11 | 5579965600 |
| 12 | 85018056640 |
| 13 | 1380373170880 |
| 14 | 23792373137280 |
| 15 | 433881469662080 |
| 16 | 8346202841391360 |
| 17 | 168894762064666880 |
| 18 | 3586667489988830720 |
| 19 | 79753496814542988800 |