The cototient of a positive number is defined as , where is the totient function.
It is therefore the number of positive integers that have at least one prime factor in common with .
The first few cototients for ,
2, ... are 0, 1, 1, 2, 1, 4, 1, 4, 3, 6, 1, 8, 1, 8, 7, ... (OEIS A051953).
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A. and Luca, F. "Infinite Families of Noncototients." Colloq. Math.86,
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Sequence A051953 in "The On-Line Encyclopedia
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