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 | 1 |
| 2 | 1 |
| 3 | 9 |
| 4 | 252 |
| 5 | 16380 |
| 6 | 2063880 |
| 7 | 447861960 |
| 8 | 154064514240 |
| 9 | 79035095805120 |
| 10 | 57695619937737600 |
| 11 | 57753315557675337600 |
| 12 | 76927416322823549683200 |
| 13 | 133007502822161917402252800 |
| 14 | 292350491203111894450151654400 |
| 15 | 802502098352542150265666291328000 |