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 | -1 |
| 2 | 7 |
| 3 | -31 |
| 4 | 127 |
| 5 | -511 |
| 6 | 1414477 |
| 7 | -8191 |
| 8 | 118518239 |
| 9 | -5749691557 |
| 10 | 91546277357 |
| 11 | -23273283019 |
| 12 | 1982765468311237 |
| 13 | -22076500342261 |
| 14 | 455371239541065869 |
| 15 | -925118910976041358111 |
| 16 | 16555640865486520478399 |
| 17 | -1302480594081611886641 |
| 18 | 904185845619475242495834469891 |