Count Good Numbers
A digit string is good if the digits (0-indexed) at even indices are even and the digits at odd indices are prime (2, 3, 5, or 7).
A digit string is good if the digits (0-indexed) at even indices are even and the digits at odd indices are prime (2, 3, 5, or 7).
Given an integer n, return the total number of good digit strings of length n. Since the answer may be large, return it modulo 10^9 + 7.
A digit string is a string consisting of digits 0 through 9 that may contain leading zeros.
Example 1
Input: n = 1
Output: 5
Explanation: The good numbers of length 1 are "0", "2", "4", "6", "8".
Example 2
Input: n = 4
Output: 400
Example 3
Input: n = 50
Output: 564908303
Constraints
- 1 <= n <= 1015
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