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 | -3 |
| 4 | -1 |
| 5 | -7 |
| 6 | -1 |
| 7 | -15 |
| 8 | 31 |
| 9 | -63 |
| 10 | 159 |
| 11 | -95 |
| 12 | 671 |
| 13 | -287 |
| 14 | 3231 |
| 15 | -2975 |
| 16 | 15519 |
| 17 | -7839 |
| 18 | 44191 |
| 19 | -34975 |
| 20 | 224415 |
| 21 | -291999 |
| 22 | 863391 |
| 23 | -990367 |
| 24 | 2927775 |
| 25 | -4902047 |
| 26 | 12561567 |
| 27 | -27225247 |
| 28 | 56470687 |
| 29 | -102640799 |
| 30 | 152153247 |
| 31 | -422620319 |
| 32 | 877243551 |
| 33 | -2278272159 |
| 34 | 3357125791 |