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 | 1 |
| 3 | 8 |
| 4 | 78 |
| 5 | 944 |
| 6 | 13800 |
| 7 | 237432 |
| 8 | 4708144 |
| 9 | 105822432 |
| 10 | 2660215680 |
| 11 | 73983185000 |
| 12 | 2255828154624 |
| 13 | 74841555118992 |
| 14 | 2684366717713408 |
| 15 | 103512489775594200 |
| 16 | 4270718991667353600 |
| 17 | 187728592242564421568 |
| 18 | 8759085548690928992256 |
| 19 | 432357188322752488126152 |
| 20 | 22510748754252398927872000 |