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 | 19 |
| 3 | 199 |
| 4 | 1999 |
| 5 | 19999 |
| 6 | 199999 |
| 7 | 1999999 |
| 8 | 19999999 |
| 9 | 199999999 |
| 10 | 1999999999 |
| 11 | 19999999999 |
| 12 | 199999999999 |
| 13 | 1999999999999 |
| 14 | 19999999999999 |
| 15 | 199999999999999 |
| 16 | 1999999999999999 |
| 17 | 19999999999999999 |
| 18 | 199999999999999999 |
| 19 | 1999999999999999999 |
| 20 | 19999999999999999999 |
| 21 | 199999999999999999999 |