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 | 2 |
| 1 | 9 |
| 2 | 101 |
| 3 | 999 |
| 4 | 10001 |
| 5 | 99999 |
| 6 | 1000001 |
| 7 | 9999999 |
| 8 | 100000001 |
| 9 | 999999999 |
| 10 | 10000000001 |
| 11 | 99999999999 |
| 12 | 1000000000001 |
| 13 | 9999999999999 |
| 14 | 100000000000001 |
| 15 | 999999999999999 |
| 16 | 10000000000000001 |
| 17 | 99999999999999999 |
| 18 | 1000000000000000001 |
| 19 | 9999999999999999999 |
| 20 | 100000000000000000001 |