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 | 18315 |
| 3 | 142010 |
| 4 | 457380 |
| 5 | 809424 |
| 6 | 2044350 |
| 7 | 237600 |
| 8 | 2494800 |
| 9 | 2217600 |
| 10 | 498960 |
| 11 | 3628800 |
| 12 | 2910600 |
| 13 | 0 |
| 14 | 712800 |
| 15 | 887040 |
| 16 | 0 |
| 17 | 0 |
| 18 | 0 |
| 19 | 0 |
| 20 | 997920 |
| 21 | 1900800 |