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 | 6 |
| 2 | 20 |
| 3 | 120 |
| 4 | 272 |
| 5 | 1632 |
| 6 | 5440 |
| 7 | 32640 |
| 8 | 65792 |
| 9 | 394752 |
| 10 | 1315840 |
| 11 | 7895040 |
| 12 | 17895424 |
| 13 | 107372544 |
| 14 | 357908480 |
| 15 | 2147450880 |
| 16 | 4295032832 |
| 17 | 25770196992 |
| 18 | 85900656640 |
| 19 | 515403939840 |
| 20 | 1168248930304 |
| 21 | 7009493581824 |
| 22 | 23364978606080 |