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 | -5 |
| 2 | -21 |
| 3 | -21 |
| 4 | 89 |
| 5 | 377 |
| 6 | 377 |
| 7 | -1597 |
| 8 | -6765 |
| 9 | -6765 |
| 10 | 28657 |
| 11 | 121393 |
| 12 | 121393 |
| 13 | -514229 |
| 14 | -2178309 |
| 15 | -2178309 |
| 16 | 9227465 |
| 17 | 39088169 |
| 18 | 39088169 |
| 19 | -165580141 |
| 20 | -701408733 |
| 21 | -701408733 |
| 22 | 2971215073 |
| 23 | 12586269025 |
| 24 | 12586269025 |
| 25 | -53316291173 |
| 26 | -225851433717 |
| 27 | -225851433717 |