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 | 1 |
| 2 | 37 |
| 3 | 397 |
| 4 | 3997 |
| 5 | 39997 |
| 6 | 399997 |
| 7 | 3999997 |
| 8 | 39999997 |
| 9 | 399999997 |
| 10 | 3999999997 |
| 11 | 39999999997 |
| 12 | 399999999997 |
| 13 | 3999999999997 |
| 14 | 39999999999997 |
| 15 | 399999999999997 |
| 16 | 3999999999999997 |
| 17 | 39999999999999997 |
| 18 | 399999999999999997 |
| 19 | 3999999999999999997 |
| 20 | 39999999999999999997 |
| 21 | 399999999999999999997 |