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 | 2 |
| 2 | 11 |
| 3 | -1 |
| 4 | 10010101 |
| 5 | 1000011011 |
| 6 | -1 |
| 7 | 10000101011101 |
| 8 | 1000000010111111 |
| 9 | -1 |
| 10 | 10000000011111011101 |
| 11 | 1000000000101101111111 |
| 12 | -1 |
| 13 | 10000000000001111011111111 |
| 14 | 1000000000000111111101110111 |
| 15 | -1 |
| 16 | 10000000000000011101111111011111 |
| 17 | 1000000000000000010111111111111111 |
| 18 | -1 |