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 | 0 |
| 2 | 0 |
| 3 | 3 |
| 4 | 12 |
| 5 | 120 |
| 6 | 1200 |
| 7 | 16380 |
| 8 | 255696 |
| 9 | 4726008 |
| 10 | 99107280 |
| 11 | 2346042600 |
| 12 | 61706210280 |
| 13 | 1788467429892 |
| 14 | 56618211155688 |
| 15 | 1944581982268380 |
| 16 | 72019509651227040 |
| 17 | 2861473883255362800 |
| 18 | 121414006972684901664 |
| 19 | 5479661140682410928592 |
| 20 | 262122044885503316203320 |