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) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | -1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | -1 |
| 7 | 3 |
| 8 | 1 |
| 9 | 5 |
| 10 | -1 |
| 11 | 11 |
| 12 | 1 |
| 13 | 21 |
| 14 | -1 |
| 15 | 43 |
| 16 | 1 |
| 17 | 85 |
| 18 | -1 |
| 19 | 171 |
| 20 | 1 |
| 21 | 341 |
| 22 | -1 |
| 23 | 683 |
| 24 | 1 |
| 25 | 1365 |
| 26 | -1 |
| 27 | 2731 |
| 28 | 1 |
| 29 | 5461 |
| 30 | -1 |
| 31 | 10923 |
| 32 | 1 |
| 33 | 21845 |
| 34 | -1 |
| 35 | 43691 |
| 36 | 1 |
| 37 | 87381 |
| 38 | -1 |
| 39 | 174763 |
| 40 | 1 |
| 41 | 349525 |
| 42 | -1 |
| 43 | 699051 |
| 44 | 1 |
| 45 | 1398101 |
| 46 | -1 |
| 47 | 2796203 |
| 48 | 1 |
| 49 | 5592405 |
| 50 | -1 |
| 51 | 11184811 |
| 52 | 1 |
| 53 | 22369621 |
| 54 | -1 |
| 55 | 44739243 |
| 56 | 1 |