{ "data": { "question": { "questionId": "446", "questionFrontendId": "446", "boundTopicId": null, "title": "Arithmetic Slices II - Subsequence", "titleSlug": "arithmetic-slices-ii-subsequence", "content": "

Given an integer array nums, return the number of all the arithmetic subsequences of nums.

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A sequence of numbers is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the same.

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A subsequence of an array is a sequence that can be formed by removing some elements (possibly none) of the array.

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The test cases are generated so that the answer fits in 32-bit integer.

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Example 1:

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\nInput: nums = [2,4,6,8,10]\nOutput: 7\nExplanation: All arithmetic subsequence slices are:\n[2,4,6]\n[4,6,8]\n[6,8,10]\n[2,4,6,8]\n[4,6,8,10]\n[2,4,6,8,10]\n[2,6,10]\n
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Example 2:

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\nInput: nums = [7,7,7,7,7]\nOutput: 16\nExplanation: Any subsequence of this array is arithmetic.\n
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Constraints:

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