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 | 21 |
| 3 | 123 |
| 4 | 4321 |
| 5 | 12345 |
| 6 | 654321 |
| 7 | 1234567 |
| 8 | 87654321 |
| 9 | 123456789 |
| 10 | 10987654321 |
| 11 | 1234567891011 |
| 12 | 121110987654321 |
| 13 | 12345678910111213 |
| 14 | 1413121110987654321 |
| 15 | 123456789101112131415 |