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 | 0 |
| 1 | 4 |
| 2 | 56 |
| 3 | 660 |
| 4 | 7280 |
| 5 | 77520 |
| 6 | 807576 |
| 7 | 8288280 |
| 8 | 84146400 |
| 9 | 847289520 |
| 10 | 8476605280 |
| 11 | 84362730452 |
| 12 | 836022413616 |
| 13 | 8255176274800 |
| 14 | 81266247493200 |
| 15 | 797911337890800 |
| 16 | 7816430993273280 |
| 17 | 76417576884236016 |
| 18 | 745777615780501920 |
| 19 | 7266758081613043600 |
| 20 | 70706322844243486400 |
| 21 | 687103929058903836480 |