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 | 3 |
| 2 | 15 |
| 3 | 120 |
| 4 | 1320 |
| 5 | 2640 |
| 6 | 50160 |
| 7 | 50160 |
| 8 | 451440 |
| 9 | 902880 |
| 10 | 11737440 |
| 11 | 82162080 |
| 12 | 575134560 |
| 13 | 575134560 |
| 14 | 575134560 |
| 15 | 17829171360 |
| 16 | 410070941280 |
| 17 | 410070941280 |
| 18 | 32395604361120 |
| 19 | 1393010987528160 |
| 20 | 1393010987528160 |
| 21 | 65471516413823520 |