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 | 3 |
| 1 | 4 |
| 2 | 7 |
| 3 | 15 |
| 4 | 32 |
| 5 | 65 |
| 6 | 129 |
| 7 | 256 |
| 8 | 511 |
| 9 | 1023 |
| 10 | 2048 |
| 11 | 4097 |
| 12 | 8193 |
| 13 | 16384 |
| 14 | 32767 |
| 15 | 65535 |
| 16 | 131072 |
| 17 | 262145 |
| 18 | 524289 |
| 19 | 1048576 |
| 20 | 2097151 |
| 21 | 4194303 |
| 22 | 8388608 |
| 23 | 16777217 |
| 24 | 33554433 |
| 25 | 67108864 |
| 26 | 134217727 |
| 27 | 268435455 |
| 28 | 536870912 |
| 29 | 1073741825 |
| 30 | 2147483649 |