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 | 2 |
| 2 | -1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 17 |
| 6 | -1 |
| 7 | 271 |
| 8 | 1 |
| 9 | 7937 |
| 10 | -1 |
| 11 | 353791 |
| 12 | 1 |
| 13 | 22368257 |
| 14 | -1 |
| 15 | 1903757311 |
| 16 | 1 |
| 17 | 209865342977 |
| 18 | -1 |
| 19 | 29088885112831 |
| 20 | 1 |
| 21 | 4951498053124097 |
| 22 | -1 |
| 23 | 1015423886506852351 |
| 24 | 1 |
| 25 | 246921480190207983617 |
| 26 | -1 |
| 27 | 70251601603943959887871 |
| 28 | 1 |
| 29 | 23119184187809597841473537 |