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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | -2 |
| 4 | 4 |
| 5 | -8 |
| 6 | 16 |
| 7 | -32 |
| 8 | 64 |
| 9 | -128 |
| 10 | 256 |
| 11 | -512 |
| 12 | 1024 |
| 13 | -2048 |
| 14 | 4096 |
| 15 | -8192 |
| 16 | 16384 |
| 17 | -32768 |
| 18 | 65536 |
| 19 | -131072 |
| 20 | 262144 |
| 21 | -524288 |
| 22 | 1048576 |
| 23 | -2097151 |
| 24 | 4194280 |
| 25 | -8388307 |
| 26 | 16774590 |
| 27 | -33536530 |
| 28 | 67007280 |
| 29 | -133718550 |
| 30 | 266253060 |
| 31 | -528213975 |
| 32 | 1042120800 |
| 33 | -2039889435 |