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) |
|---|---|
| 2 | 2 |
| 3 | 6 |
| 4 | 36 |
| 5 | 270 |
| 6 | 2244 |
| 7 | 19740 |
| 8 | 179880 |
| 9 | 1678446 |
| 10 | 15927780 |
| 11 | 153055188 |
| 12 | 1485010488 |
| 13 | 14518525164 |
| 14 | 142821228648 |
| 15 | 1412109087480 |
| 16 | 14021321053392 |
| 17 | 139725123309486 |
| 18 | 1396698760714788 |
| 19 | 13998927825197220 |
| 20 | 140638610864578200 |