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 | 9 |
| 2 | 99 |
| 3 | 333 |
| 4 | 999 |
| 5 | 3663 |
| 6 | 9999 |
| 7 | 12321 |
| 8 | 30303 |
| 9 | 36963 |
| 10 | 99999 |
| 11 | 135531 |
| 12 | 333333 |
| 13 | 369963 |
| 14 | 999999 |
| 15 | 1121211 |
| 16 | 1367631 |
| 17 | 3003003 |
| 18 | 3363633 |
| 19 | 3699963 |
| 20 | 9999999 |
| 21 | 12333321 |
| 22 | 13688631 |
| 23 | 33033033 |
| 24 | 33666633 |
| 25 | 36999963 |
| 26 | 99999999 |
| 27 | 102030201 |
| 28 | 111111111 |
| 29 | 124454421 |
| 30 | 136898631 |
| 31 | 300030003 |