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 | 1 |
| 2 | 3 |
| 3 | 20 |
| 4 | 30 |
| 5 | 336 |
| 6 | 5040 |
| 7 | 7920 |
| 8 | 154440 |
| 9 | 3603600 |
| 10 | 5765760 |
| 11 | 160392960 |
| 12 | 5079110400 |
| 13 | 8204716800 |
| 14 | 296541907200 |
| 15 | 11861676288000 |
| 16 | 520431047136000 |
| 17 | 857180548224000 |
| 18 | 41430393164160000 |
| 19 | 2163102632570880000 |
| 20 | 3569119343741952000 |