The Number of Quadratic Residues
The list of the number of quadratic residues mod n, for n=1,2,3..., looks like:
- 1, 2, 2, 2, 3, 4, 4, 3, 4, 6, 6, 4, 7, 8, 6, 4, 9, 8, 10, 6, 8, 12, 12, 6, 11, 14, 11, 8, 15, 12, 16, 7, 12, 18, 12, 8, 19, 20, 14, 9, 21, 16, 22, 12, 12, 24, 24, 8, 22, 22, 18, 14, 27, 22, 18, 12, 20, 30, 30, 12, 31, 32, 16, 12, 21, ...
A formula to count the number of squares mod n is given by Stangl.
Read more about this topic: Quadratic Residue
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