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 | 4 |
| 2 | -11 |
| 3 | 30 |
| 4 | -83 |
| 5 | 232 |
| 6 | -654 |
| 7 | 1856 |
| 8 | -5296 |
| 9 | 15180 |
| 10 | -43675 |
| 11 | 126062 |
| 12 | -364863 |
| 13 | 1058552 |
| 14 | -3077533 |
| 15 | 8963862 |
| 16 | -26151753 |
| 17 | 76409052 |
| 18 | -223544241 |
| 19 | 654790218 |
| 20 | -1920055017 |
| 21 | 5635816776 |
| 22 | -16557539124 |
| 23 | 48685404516 |
| 24 | -143264248974 |
| 25 | 421879104836 |
| 26 | -1243160223829 |
| 27 | 3665516301186 |