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) |
|---|---|
| 4 | 1 |
| 5 | 25 |
| 6 | 1227 |
| 7 | 84672 |
| 8 | 7635120 |
| 9 | 850626360 |
| 10 | 112876089480 |
| 11 | 17381709797760 |
| 12 | 3046480841900160 |
| 13 | 598731545755324800 |
| 14 | 130389773403373545600 |
| 15 | 31163616486434838067200 |
| 16 | 8109213009296586130944000 |
| 17 | 2282014010657773764160588800 |
| 18 | 690521215428258768326957184000 |