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 | 4 |
| 2 | 44 |
| 3 | 444 |
| 4 | 4444 |
| 5 | 44444 |
| 6 | 444444 |
| 7 | 4444444 |
| 8 | 44444444 |
| 9 | 444444444 |
| 10 | 4444444444 |
| 11 | 44444444444 |
| 12 | 444444444444 |
| 13 | 4444444444444 |
| 14 | 44444444444444 |
| 15 | 444444444444444 |
| 16 | 4444444444444444 |
| 17 | 44444444444444444 |
| 18 | 444444444444444444 |
| 19 | 4444444444444444444 |
| 20 | 44444444444444444444 |
| 21 | 444444444444444444444 |