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 | 20 |
| 2 | 20 |
| 3 | 10 |
| 4 | 105 |
| 5 | 1512 |
| 6 | 27720 |
| 7 | 4620 |
| 8 | 660 |
| 9 | 144144 |
| 10 | 16016 |
| 11 | 5445440 |
| 12 | 495040 |
| 13 | 12697776 |
| 14 | 976752 |
| 15 | 69768 |
| 16 | 823727520 |
| 17 | 51482970 |
| 18 | 3028410 |
| 19 | 168245 |
| 20 | 8855 |
| 21 | 159845400 |
| 22 | 5768642880 |
| 23 | 262211040 |
| 24 | 11400480 |
| 25 | 475020 |
| 26 | 543814622208 |
| 27 | 20915947008 |
| 28 | 774664704 |
| 29 | 941432800 |