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 | 1 |
| 3 | 4 |
| 4 | 13 |
| 5 | 44 |
| 6 | 148 |
| 7 | 498 |
| 8 | 1676 |
| 9 | 5640 |
| 10 | 18980 |
| 11 | 63872 |
| 12 | 214944 |
| 13 | 723336 |
| 14 | 2434192 |
| 15 | 8191616 |
| 16 | 27566672 |
| 17 | 92768192 |
| 18 | 312186304 |
| 19 | 1050578720 |
| 20 | 3535439040 |
| 21 | 11897565568 |
| 22 | 40038044736 |
| 23 | 134737229824 |
| 24 | 453421769728 |
| 25 | 1525868548224 |
| 26 | 5134898635008 |
| 27 | 17280115002368 |
| 28 | 58151561641216 |