Circular Permutation in Binary

Generate a circular Gray code sequence of length 2^n starting from a given start value. In this cyclic sequence, adjacent numbers (including the first and last) differ by exactly one bit in binary. Return the sequence as a permutation of all integers from 0 to 2^n - 1.

Examples
Input: [2,3]
Output: [3,2,0,1]
Hints

Circular Permutation in Binary

Generate a circular Gray code sequence of length `2^n` starting from a given `start` value. In this cyclic sequence, adjacent numbers (including the first and last) differ by exactly one bit in binary. Return the sequence as a permutation of all integers from 0 to 2^n - 1.