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 | 11 |
| 2 | 99 |
| 3 | 1001 |
| 4 | 9999 |
| 5 | 100001 |
| 6 | 999999 |
| 7 | 10000001 |
| 8 | 99999999 |
| 9 | 1000000001 |
| 10 | 9999999999 |
| 11 | 100000000001 |
| 12 | 999999999999 |
| 13 | 10000000000001 |
| 14 | 99999999999999 |
| 15 | 1000000000000001 |
| 16 | 9999999999999999 |
| 17 | 100000000000000001 |
| 18 | 999999999999999999 |
| 19 | 10000000000000000001 |