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 | 0 |
| 5 | 60 |
| 6 | 900 |
| 7 | 8400 |
| 8 | 63000 |
| 9 | 417120 |
| 10 | 2551500 |
| 11 | 14804700 |
| 12 | 82764000 |
| 13 | 450518460 |
| 14 | 2404502100 |
| 15 | 12646078140 |
| 16 | 65771433000 |
| 17 | 339165516120 |
| 18 | 1737485731740 |
| 19 | 8855359634100 |
| 20 | 44952365429940 |
| 21 | 227475768899460 |