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 | 0 |
| 4 | 24 |
| 5 | 144 |
| 6 | 1398 |
| 7 | 11184 |
| 8 | 97200 |
| 9 | 973296 |
| 10 | 10950696 |
| 11 | 131408352 |
| 12 | 1593191808 |
| 13 | 22304685312 |
| 14 | 333297226080 |
| 15 | 5103130001760 |
| 16 | 81686161277280 |
| 17 | 1470350902991040 |
| 18 | 26490792085668288 |
| 19 | 529815841713365760 |
| 20 | 10635027891469974720 |