Summary
The full combinations of 4 to 9 distinctive numbers, minus the combinations which include invalid “jump”s.
The Long Version
The rule for Android 3×3 password grid:
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one point for once
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cannot “jump” over a point
The author of the original post used Mathematica to generate all 985824 combinations.
Because there is no “jump”, several pairs of consecutive points are invalid.
Delete all invalid combinations to reach the result.
The combinations for 4-to-9-point paths are respectively 1624, 7152, 26016, 72912, 140704, 140704.
The Original Post In Chinese
The reference is from guokr, a site alike Stack Exchange Skeptics in the form of blogs.