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 | 6 |
| 3 | 30 |
| 4 | 330 |
| 5 | 390 |
| 6 | 2730 |
| 7 | 5460 |
| 8 | 12090 |
| 9 | 60060 |
| 10 | 92820 |
| 11 | 223860 |
| 12 | 1021020 |
| 13 | 1922700 |
| 14 | 3805620 |
| 15 | 13458900 |
| 16 | 41861820 |
| 17 | 110362980 |
| 18 | 113573460 |
| 19 | 227146920 |
| 20 | 251170920 |
| 21 | 502341840 |
| 22 | 563603040 |
| 23 | 888287400 |
| 24 | 1270629360 |
| 25 | 1776574800 |
| 26 | 3310889400 |
| 27 | 23107724640 |
| 28 | 27939071160 |
| 29 | 33754921200 |
| 30 | 36419783400 |