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 | 4 |
| 2 | 6 |
| 3 | 16 |
| 4 | 48 |
| 5 | 142 |
| 6 | 472 |
| 7 | 1670 |
| 8 | 6364 |
| 9 | 24604 |
| 10 | 97668 |
| 11 | 390070 |
| 12 | 1570560 |
| 13 | 6334644 |
| 14 | 25617062 |
| 15 | 103669288 |
| 16 | 419930444 |
| 17 | 1701635046 |
| 18 | 6898183050 |