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) |
|---|---|
| 0 | 4 |
| 1 | 747 |
| 2 | 77477 |
| 3 | 7774777 |
| 4 | 777747777 |
| 5 | 77777477777 |
| 6 | 7777774777777 |
| 7 | 777777747777777 |
| 8 | 77777777477777777 |
| 9 | 7777777774777777777 |
| 10 | 777777777747777777777 |
| 11 | 77777777777477777777777 |
| 12 | 7777777777774777777777777 |
| 13 | 777777777777747777777777777 |
| 14 | 77777777777777477777777777777 |
| 15 | 7777777777777774777777777777777 |