/**
 * Maps an index to a palindrome pattern.
 * @param index The original index.
 * @param length The length of the sequence.
 * @returns The mapped index in the palindrome pattern.
 * @example
 * const length = 5
 * const indexes = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
 * indexes.map((index) => palindrome(index, length))
 * // Returns [0, 1, 2, 1, 0, 1, 2, 1, 0, 1]
 */
export declare const palindrome: (index: number, length: number) => number;