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) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 4320 |
| 3 | 61440 |
| 4 | 522720 |
| 5 | 2211840 |
| 6 | 8960640 |
| 7 | 23224320 |
| 8 | 67154400 |
| 9 | 135168000 |
| 10 | 319809600 |
| 11 | 550195200 |
| 12 | 1147643520 |
| 13 | 1771683840 |
| 14 | 3371915520 |
| 15 | 4826603520 |
| 16 | 8593797600 |
| 17 | 11585617920 |
| 18 | 19590534240 |
| 19 | 25239859200 |
| 20 | 40979580480 |
| 21 | 50877235200 |