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 | 1 |
| 2 | 4 |
| 3 | 32 |
| 4 | 288 |
| 5 | 4608 |
| 6 | 115200 |
| 7 | 3110400 |
| 8 | 99532800 |
| 9 | 3583180800 |
| 10 | 175575859200 |
| 11 | 11236854988800 |
| 12 | 910185254092800 |
| 13 | 91018525409280000 |
| 14 | 11013241574522880000 |
| 15 | 1376655196815360000000 |
| 16 | 176211865192366080000000 |
| 17 | 25374508587700715520000000 |
| 18 | 4288291951321420922880000000 |
| 19 | 840505222458998500884480000000 |
| 20 | 181549128051143676191047680000000 |