Given an array of unique integers, each integer is strictly greater than 1.
We make a binary tree using these integersand each number may be used for any number of times.
Each non-leaf node'svalue should be equal to the product of the values of it's children.
How many binary trees can we make? Return the answer modulo 10 ** 9 + 7.
Example 1:
Input: A = [2, 4]
Output: 3
Explanation: We can make these trees: [2], [4], [4, 2, 2]
Example 2:
Input: A = [2, 4, 5, 10]
Output: 7
Explanation: We can make these trees: [2], [4], [5], [10], [4, 2, 2], [10, 2, 5], [10, 5, 2].
Note:
- 1 <= A.length <=1000.
- 2 <=A[i]<=10 ^ 9.
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