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A242444 Number of squares k^2 < n with k^2*p == 1 (mod n) for some prime p < n. 4
0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 2, 0, 1, 1, 0, 0, 2, 0, 2, 0, 0, 1, 1, 0, 2, 1, 2, 0, 2, 0, 3, 0, 1, 1, 1, 1, 2, 1, 0, 0, 2, 1, 2, 2, 1, 1, 2, 0, 3, 0, 1, 2, 2, 2, 1, 0, 2, 2, 2, 0, 1, 3, 0, 2, 2, 2, 2, 1, 2, 0, 2, 0, 2, 2, 2, 2, 3, 1, 3, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,11
COMMENTS
According to the conjecture in A242441, a(n) > 0 for all n > 1848.
LINKS
EXAMPLE
a(9) = 1 since 2^2*7 == 1 (mod 9).
MATHEMATICA
r[k_, n_]:=PowerMod[k^2, -1, n]
Do[m=0; Do[If[GCD[k, n]==1&&PrimeQ[r[k, n]], m=m+1], {k, 1, Sqrt[n-1]}]; Print[n, " ", m]; Continue, {n, 1, 80}]
CROSSREFS
Sequence in context: A302233 A214772 A332036 * A236441 A327695 A345446
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, May 14 2014
STATUS
approved

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Last modified August 23 20:14 EDT 2024. Contains 375396 sequences. (Running on oeis4.)