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 | 6 |
| 2 | 20 |
| 3 | 72 |
| 4 | 272 |
| 5 | 2808 |
| 6 | 5280 |
| 7 | 12480 |
| 8 | 65792 |
| 9 | 251719680 |
| 10 | 4295032832 |
| 11 | 39462420480 |
| 12 | 2151811200000 |
| 13 | 375297105592320 |
| 14 | 4238621367336960 |
| 15 | 20203489717239782783648394117120 |
| 16 | 84353101158454670682576150304666023245622804480 |