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 | 3 |
| 2 | 53 |
| 3 | 547 |
| 4 | 5531 |
| 5 | 55547 |
| 6 | 555523 |
| 7 | 5555527 |
| 8 | 55555553 |
| 9 | 555555541 |
| 10 | 5555555519 |
| 11 | 55555555543 |
| 12 | 555555555551 |
| 13 | 5555555555551 |
| 14 | 55555555555541 |
| 15 | 555555555555529 |
| 16 | 5555555555555539 |
| 17 | 55555555555555519 |
| 18 | 555555555555555487 |
| 19 | 5555555555555555533 |
| 20 | 55555555555555555483 |
| 21 | 555555555555555555491 |