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 | 7 |
| 2 | 47 |
| 3 | 4007 |
| 4 | 4447 |
| 5 | 7477 |
| 6 | 44777 |
| 7 | 47407 |
| 8 | 47777 |
| 9 | 74047 |
| 10 | 74077 |
| 11 | 74707 |
| 12 | 74747 |
| 13 | 77047 |
| 14 | 77447 |
| 15 | 77477 |
| 16 | 77747 |
| 17 | 407047 |
| 18 | 407707 |
| 19 | 407747 |
| 20 | 440047 |
| 21 | 444007 |
| 22 | 444047 |
| 23 | 470077 |
| 24 | 470447 |
| 25 | 474077 |
| 26 | 474707 |
| 27 | 477047 |
| 28 | 477077 |
| 29 | 704447 |
| 30 | 704477 |
| 31 | 704747 |
| 32 | 704777 |
| 33 | 707407 |
| 34 | 707747 |
| 35 | 740477 |
| 36 | 744077 |
| 37 | 744407 |
| 38 | 744707 |
| 39 | 747407 |
| 40 | 770047 |