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) |
|---|---|
| 3 | 1 |
| 4 | 12 |
| 5 | 130 |
| 6 | 1380 |
| 7 | 15435 |
| 8 | 182280 |
| 9 | 2302020 |
| 10 | 30958200 |
| 11 | 444230325 |
| 12 | 6771510900 |
| 13 | 109568809350 |
| 14 | 1874844071100 |
| 15 | 33875023557375 |
| 16 | 644264598978000 |
| 17 | 12877256933541000 |
| 18 | 269789087886318000 |
| 19 | 5915648230774907625 |
| 20 | 135459771081512377500 |
| 21 | 3234745039813583546250 |