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 | 6 |
| 2 | 30 |
| 3 | 216 |
| 4 | 1500 |
| 5 | 12960 |
| 6 | 77760 |
| 7 | 948192 |
| 8 | 7344000 |
| 9 | 72071856 |
| 10 | 589032000 |
| 11 | 6060314304 |
| 12 | 38491200000 |
| 13 | 496775732544 |
| 14 | 4309959326400 |
| 15 | 40676940288000 |
| 16 | 345599944704000 |
| 17 | 3921566733817776 |
| 18 | 24555273410096640 |
| 19 | 350877192982456140 |
| 20 | 2915072245440000000 |