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 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 12 |
| 6 | 56 |
| 7 | 456 |
| 8 | 6880 |
| 9 | 191536 |
| 10 | 9733056 |
| 11 | 903753248 |
| 12 | 154108311168 |
| 13 | 48542114686912 |
| 14 | 28401423719122304 |
| 15 | 31021002160355166848 |
| 16 | 63530415842308265100288 |
| 17 | 244912778438520759443245824 |
| 18 | 1783398846284777975419600287232 |
| 19 | 24605641171260376770598003978281472 |