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 | 3 |
| 3 | 9 |
| 4 | 111 |
| 5 | 333 |
| 6 | 999 |
| 7 | 12321 |
| 8 | 36963 |
| 9 | 1001001 |
| 10 | 3003003 |
| 11 | 9009009 |
| 12 | 111111111 |
| 13 | 333333333 |
| 14 | 999999999 |
| 15 | 12333333321 |
| 16 | 36999999963 |
| 17 | 1002003002001 |
| 18 | 3006009006003 |
| 19 | 111222333222111 |
| 20 | 333666999666333 |
| 21 | 12345678987654321 |