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 | -2 |
| 3 | 1 |
| 4 | -5 |
| 5 | 16 |
| 6 | -35 |
| 7 | 67 |
| 8 | -128 |
| 9 | 253 |
| 10 | -509 |
| 11 | 1024 |
| 12 | -2051 |
| 13 | 4099 |
| 14 | -8192 |
| 15 | 16381 |
| 16 | -32765 |
| 17 | 65536 |
| 18 | -131075 |
| 19 | 262147 |
| 20 | -524288 |
| 21 | 1048573 |
| 22 | -2097149 |
| 23 | 4194304 |
| 24 | -8388611 |
| 25 | 16777219 |
| 26 | -33554432 |
| 27 | 67108861 |
| 28 | -134217725 |
| 29 | 268435456 |