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 | 0 |
| 5 | 0 |
| 6 | 15 |
| 7 | 315 |
| 8 | 4200 |
| 9 | 45360 |
| 10 | 433440 |
| 11 | 3825360 |
| 12 | 31944000 |
| 13 | 256164480 |
| 14 | 1991877888 |
| 15 | 15117822720 |
| 16 | 112519680000 |
| 17 | 824063385600 |
| 18 | 5953789181952 |
| 19 | 42518284701696 |
| 20 | 300588079104000 |
| 21 | 2106258635980800 |
| 22 | 14642876032942080 |
| 23 | 101081482775691264 |
| 24 | 693338799538176000 |
| 25 | 4728258324725760000 |
| 26 | 32074214121878323200 |