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 | 7 |
| 3 | -17 |
| 4 | 63 |
| 5 | -161 |
| 6 | 543 |
| 7 | -1377 |
| 8 | 4255 |
| 9 | -11105 |
| 10 | 31903 |
| 11 | -82785 |
| 12 | 232607 |
| 13 | -594785 |
| 14 | 1617055 |
| 15 | -4150113 |
| 16 | 10988703 |
| 17 | -27939681 |
| 18 | 72985759 |
| 19 | -183915361 |
| 20 | 473541791 |
| 21 | -1187402593 |
| 22 | 3015290015 |
| 23 | -7512413025 |
| 24 | 18911702175 |
| 25 | -46787875681 |
| 26 | 116689317023 |
| 27 | -287306044257 |