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 | 5 |
| 4 | -23 |
| 5 | -41 |
| 6 | 1111 |
| 7 | -6259 |
| 8 | -16015 |
| 9 | 828143 |
| 10 | -6453809 |
| 11 | -23557931 |
| 12 | 1516982809 |
| 13 | -15821700025 |
| 14 | -76745280793 |
| 15 | 5613303472349 |
| 16 | -73951449390239 |
| 17 | -445513157340449 |
| 18 | 36776986711862815 |
| 19 | -582726291386478427 |
| 20 | -4158268555818657079 |
| 21 | 388618610293537423799 |