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) |
|---|---|
| 3 | 1 |
| 4 | 1 |
| 5 | 10 |
| 6 | 180 |
| 7 | 4620 |
| 8 | 152880 |
| 9 | 6168960 |
| 10 | 293025600 |
| 11 | 15990004800 |
| 12 | 984647664000 |
| 13 | 67493121696000 |
| 14 | 5094263446272000 |
| 15 | 419688934689024000 |
| 16 | 37465564582397952000 |
| 17 | 3601861863990534144000 |
| 18 | 370962724717928318976000 |
| 19 | 40744403224500159055872000 |