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 | 4 |
| 5 | 20 |
| 6 | 120 |
| 7 | 840 |
| 8 | 6720 |
| 9 | 60480 |
| 10 | 604800 |
| 11 | 6652800 |
| 12 | 79833600 |
| 13 | 1037836800 |
| 14 | 14529715200 |
| 15 | 217945728000 |
| 16 | 3487131648000 |
| 17 | 59281238016000 |
| 18 | 1067062284288000 |
| 19 | 20274183401472000 |
| 20 | 405483668029440000 |
| 21 | 8515157028618240000 |
| 22 | 187333454629601280000 |
| 23 | 4308669456480829440000 |