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 | 1 |
| 1 | 121 |
| 2 | 12121 |
| 3 | 12321 |
| 4 | 1212121 |
| 5 | 1212321 |
| 6 | 1232121 |
| 7 | 1232321 |
| 8 | 1234321 |
| 9 | 121212121 |
| 10 | 121212321 |
| 11 | 121232121 |
| 12 | 121232321 |
| 13 | 121234321 |
| 14 | 123212121 |
| 15 | 123212321 |
| 16 | 123232121 |
| 17 | 123232321 |
| 18 | 123234321 |
| 19 | 123432121 |
| 20 | 123432321 |
| 21 | 123434321 |
| 22 | 123454321 |