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 | 3 |
| 4 | 0 |
| 5 | 0 |
| 6 | 30 |
| 7 | 84 |
| 8 | 112 |
| 9 | 720 |
| 10 | 2610 |
| 11 | 6820 |
| 12 | 29304 |
| 13 | 112632 |
| 14 | 343434 |
| 15 | 1452780 |
| 16 | 5962080 |
| 17 | 20437536 |
| 18 | 84860838 |
| 19 | 366294996 |
| 20 | 1383836500 |
| 21 | 5823855240 |
| 22 | 25918399122 |
| 23 | 105425762860 |
| 24 | 455785055328 |
| 25 | 2084426266800 |
| 26 | 8978844486300 |
| 27 | 40011097380228 |
| 28 | 187614063121716 |
| 29 | 846902215710488 |