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 | 11 |
| 1 | 3 |
| 2 | 19 |
| 3 | 139 |
| 4 | 199 |
| 5 | 1399 |
| 6 | 1999 |
| 7 | 13999 |
| 8 | 99991 |
| 9 | 139999 |
| 10 | 199999 |
| 11 | 1399999 |
| 12 | 9999991 |
| 13 | 19399999 |
| 14 | 19999999 |
| 15 | 919999939 |
| 16 | 1399939999 |
| 17 | 1999993999 |
| 18 | 9199999999 |
| 19 | 19399999999 |
| 20 | 99999199999 |
| 21 | 199999939999 |
| 22 | 991999999999 |
| 23 | 1999399999999 |