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 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 14 |
| 5 | 30 |
| 6 | 62 |
| 7 | 126 |
| 8 | 254 |
| 9 | 510 |
| 10 | 1022 |
| 11 | 2046 |
| 12 | 4094 |
| 13 | 8190 |
| 14 | 16382 |
| 15 | 32766 |
| 16 | 65534 |
| 17 | 131070 |
| 18 | 262142 |
| 19 | 524286 |
| 20 | 1048574 |
| 21 | 2097150 |
| 22 | 4194302 |
| 23 | 8388606 |
| 24 | 16777214 |
| 25 | 33554430 |
| 26 | 67108862 |
| 27 | 134217726 |
| 28 | 268435454 |
| 29 | 536870910 |
| 30 | 1073741822 |
| 31 | 2147483646 |
| 32 | 4294967294 |
| 33 | 8589934590 |
| 34 | 17179869182 |
| 35 | 34359738366 |
| 36 | 68719476734 |
| 37 | 137438953470 |