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Nonsquares mod 42.
1

%I #15 Dec 21 2019 15:55:07

%S 2,3,5,6,8,10,11,12,13,14,17,19,20,23,24,26,27,29,31,32,33,34,35,38,

%T 40,41

%N Nonsquares mod 42.

%t Complement[Range[0, 41], PowerMod[Range[42], 2, 42]] (* _Alonso del Arte_, Dec 21 2019 *)

%o (PARI) for(k=0, 42, if(!issquare(Mod(k, 42)), print1(k, ", "))) \\ _Hugo Pfoertner_, Dec 02 2019

%o (Scala) (0 to 41).diff((1 to 42).map(n => (n * n) % 42)) // _Alonso del Arte_, Dec 21 2019

%Y Cf. A010403.

%K nonn,fini,full,easy

%O 1,1

%A _N. J. A. Sloane_

%E Incorrect term 21 removed by _Alonso del Arte_, Dec 01 2019