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 | 0 |
| 1 | -1 |
| 2 | -2 |
| 3 | 0 |
| 4 | 0 |
| 5 | -128 |
| 6 | -1024 |
| 7 | 0 |
| 8 | 0 |
| 9 | -4194304 |
| 10 | -134217728 |
| 11 | 0 |
| 12 | 0 |
| 13 | -35184372088832 |
| 14 | -4503599627370496 |
| 15 | 0 |
| 16 | 0 |
| 17 | -75557863725914323419136 |
| 18 | -38685626227668133590597632 |
| 19 | 0 |
| 20 | 0 |
| 21 | -41538374868278621028243970633760768 |
| 22 | -85070591730234615865843651857942052864 |
| 23 | 0 |