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 | 1 |
| 2 | -1 |
| 3 | 5 |
| 4 | -1 |
| 5 | -1 |
| 6 | 25 |
| 7 | -5 |
| 8 | -1 |
| 9 | -1 |
| 10 | 125 |
| 11 | -25 |
| 12 | -5 |
| 13 | -1 |
| 14 | -1 |
| 15 | 625 |
| 16 | -125 |
| 17 | -25 |
| 18 | -5 |
| 19 | -1 |
| 20 | -1 |
| 21 | 3125 |
| 22 | -625 |
| 23 | -125 |
| 24 | -25 |
| 25 | -5 |
| 26 | -1 |
| 27 | -1 |
| 28 | 15625 |
| 29 | -3125 |
| 30 | -625 |
| 31 | -125 |
| 32 | -25 |
| 33 | -5 |
| 34 | -1 |
| 35 | -1 |
| 36 | 78125 |
| 37 | -15625 |
| 38 | -3125 |
| 39 | -625 |
| 40 | -125 |
| 41 | -25 |
| 42 | -5 |
| 43 | -1 |
| 44 | -1 |
| 45 | 390625 |
| 46 | -78125 |
| 47 | -15625 |
| 48 | -3125 |
| 49 | -625 |
| 50 | -125 |
| 51 | -25 |
| 52 | -5 |
| 53 | -1 |
| 54 | -1 |