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 | 16 |
| 3 | -64 |
| 4 | 256 |
| 5 | -1024 |
| 6 | 4096 |
| 7 | -16384 |
| 8 | 65536 |
| 9 | -262144 |
| 10 | 1048576 |
| 11 | -4194304 |
| 12 | 16777216 |
| 13 | -67108864 |
| 14 | 268435456 |
| 15 | -1073741824 |
| 16 | 4294967296 |
| 17 | -17179869184 |
| 18 | 68719476736 |
| 19 | -274877906944 |
| 20 | 1099511627776 |
| 21 | -4398046511104 |
| 22 | 17592186044416 |
| 23 | -70368744177664 |
| 24 | 281474976710656 |