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 | -9 |
| 3 | 91 |
| 4 | -909 |
| 5 | 9091 |
| 6 | -90909 |
| 7 | 909091 |
| 8 | -9090909 |
| 9 | 90909091 |
| 10 | -909090909 |
| 11 | 9090909091 |
| 12 | -90909090909 |
| 13 | 909090909091 |
| 14 | -9090909090909 |
| 15 | 90909090909091 |
| 16 | -909090909090909 |
| 17 | 9090909090909091 |
| 18 | -90909090909090909 |