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%I #15 Feb 01 2015 15:36:25
%S 1,2,3,4,5,6,7,8,9,11,12,14,16,20,32
%N Numbers n such that all x^2 mod n are prime powers (including 0 and 1).
%t 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 *)
%o (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
%Y Cf. A065428, A254328.
%K nonn,fini,full
%O 1,2
%A _Joerg Arndt_, Jan 28 2015
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