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 | 1 |
| 3 | 1 |
| 4 | -1 |
| 5 | 7 |
| 6 | -1 |
| 7 | 13 |
| 8 | -9 |
| 9 | 199 |
| 10 | -53 |
| 11 | 1937 |
| 12 | -373 |
| 13 | 22871 |
| 14 | -2869 |
| 15 | 4231 |
| 16 | -547 |
| 17 | 134845 |
| 18 | -1291 |
| 19 | 2425919 |
| 20 | 489967 |
| 21 | -10595393 |
| 22 | -13913 |
| 23 | 232472561 |
| 24 | 9379691 |
| 25 | -1023947321 |
| 26 | 5712079 |
| 27 | -2957435363 |
| 28 | -89098463 |
| 29 | 77729577773 |
| 30 | 93259013 |
| 31 | -2326198533397 |
| 32 | -139786038869 |
| 33 | 385098109121 |