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 | 44 |
| 3 | 744 |
| 4 | 7744 |
| 5 | 47744 |
| 6 | 447744 |
| 7 | 4447744 |
| 8 | 44447744 |
| 9 | 444447744 |
| 10 | 4444447744 |
| 11 | 74444447744 |
| 12 | 474444447744 |
| 13 | 4474444447744 |
| 14 | 44474444447744 |
| 15 | 444474444447744 |
| 16 | 7444474444447744 |
| 17 | 77444474444447744 |
| 18 | 477444474444447744 |