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 | 0 |
| 1 | 7 |
| 2 | 77 |
| 3 | 777 |
| 4 | 7777 |
| 5 | 77777 |
| 6 | 777777 |
| 7 | 7777777 |
| 8 | 77777777 |
| 9 | 777777777 |
| 10 | 7777777777 |
| 11 | 77777777777 |
| 12 | 777777777777 |
| 13 | 7777777777777 |
| 14 | 77777777777777 |
| 15 | 777777777777777 |
| 16 | 7777777777777777 |
| 17 | 77777777777777777 |
| 18 | 777777777777777777 |
| 19 | 7777777777777777777 |
| 20 | 77777777777777777777 |
| 21 | 777777777777777777777 |