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 | -1 |
| 3 | 1 |
| 4 | 7 |
| 5 | 21 |
| 6 | 51 |
| 7 | 113 |
| 8 | 239 |
| 9 | 493 |
| 10 | 1003 |
| 11 | 2025 |
| 12 | 4071 |
| 13 | 8165 |
| 14 | 16355 |
| 15 | 32737 |
| 16 | 65503 |
| 17 | 131037 |
| 18 | 262107 |
| 19 | 524249 |
| 20 | 1048535 |
| 21 | 2097109 |
| 22 | 4194259 |
| 23 | 8388561 |
| 24 | 16777167 |
| 25 | 33554381 |
| 26 | 67108811 |
| 27 | 134217673 |
| 28 | 268435399 |
| 29 | 536870853 |
| 30 | 1073741763 |
| 31 | 2147483585 |