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) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | 6 |
| 5 | 1170 |
| 6 | 64590 |
| 7 | 25153800 |
| 8 | 25153800 |
| 9 | 4747505070 |
| 10 | 207187349040 |
| 11 | 6703860240000 |
| 12 | 26997529639080 |
| 13 | 1760354281625940 |
| 14 | 1760354281625940 |
| 15 | 10718654377787155800 |