A254329 Numbers n such that all x^2 mod n are prime powers (including 0 and 1).
1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 14, 16, 20, 32
Offset: 1
Programs
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Mathematica
f[n_] := Mod[Range[n]^2, n]; Select[Range@ 10000, AllTrue[f@ #, Length@ FactorInteger[#] == 1 &] &] (* AllTrue function introduced with Version 10; Michael De Vlieger, Jan 29 2015 *)
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PARI
is(n)=for(i=2,9,if(!isprimepower(i^2%n) && i^2%n>1, return(0))); 1 \\ Charles R Greathouse IV, Jan 30 2015