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 | 2221 |
| 2 | 3331 |
| 3 | 4441 |
| 4 | 6661 |
| 5 | 1212121 |
| 6 | 1616161 |
| 7 | 2323231 |
| 8 | 2424241 |
| 9 | 2828281 |
| 10 | 3131311 |
| 11 | 3232321 |
| 12 | 3333331 |
| 13 | 3636361 |
| 14 | 3838381 |
| 15 | 4040401 |
| 16 | 4242421 |
| 17 | 4545451 |
| 18 | 5454541 |
| 19 | 5858581 |
| 20 | 6262621 |
| 21 | 6868681 |
| 22 | 6969691 |
| 23 | 7171711 |
| 24 | 7272721 |
| 25 | 8282821 |
| 26 | 9090901 |
| 27 | 9999991 |
| 28 | 1161161161 |