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 | 321 |
| 4 | 4321 |
| 5 | 54321 |
| 6 | 654321 |
| 7 | 7654321 |
| 8 | 87654321 |
| 9 | 987654321 |
| 10 | 10987654321 |
| 11 | 120987654321 |
| 12 | 1320987654321 |
| 13 | 14320987654321 |
| 14 | 154320987654321 |
| 15 | 1654320987654321 |
| 16 | 17654320987654321 |
| 17 | 187654320987654321 |
| 18 | 1987654320987654321 |
| 19 | 20987654320987654321 |
| 20 | 220987654320987654321 |