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A166715 Irregular triangle read by rows: row n lists nonzero quadratic residues modulo the n-th term of A123239.

%I A166715 #23 Feb 16 2025 08:33:11
%S A166715 1,1,1,3,4,5,9,1,3,4,9,10,12,1,3,4,7,9,10,11,12,16,21,25,26,27,28,30,
%T A166715 33,34,36,1,2,4,5,8,9,10,16,18,20,21,23,25,31,32,33,36,37,39,40,1,3,4,
%U A166715 5,7,9,12,15,16,17,19,20,21,22,25,26,27
%N A166715 Irregular triangle read by rows: row n lists nonzero quadratic residues modulo the n-th term of A123239.
%H A166715 G. C. Greubel, <a href="/A166715/b166715.txt">Table of n, a(n) for n = 1..10000</a>
%H A166715 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/QuadraticResidue.html">Quadratic Residue.</a>
%e A166715 Triangle starts:
%e A166715 1;
%e A166715 1;
%e A166715 1,3,4,5,9;
%e A166715 1,3,4,9,10,12;
%e A166715 ...
%e A166715 Modulo A123239(3)=11, the quadratic residues are 1,3,4,5,9.
%t A166715 MangammalQ[p_]:=Block[{k=3},While[k>2,k=Mod[3k,p]];k!=2];
%t A166715 A123239=Select[Prime[Range[17]],MangammalQ];
%t A166715 A166715=Flatten[Union[Mod[Range[Floor[#/2]]^2,#]]&/@A123239] (* _Ray Chandler_, Jul 21 2011 *)
%Y A166715 Cf. A046071, A063987, A123239.
%K A166715 nonn,tabf
%O A166715 1,4
%A A166715 _A.K. Devaraj_, Oct 20 2009
%E A166715 Edited by _N. J. A. Sloane_, Oct 22 2009
%E A166715 Edited by _Charles R Greathouse IV_, Oct 28 2009
%E A166715 Edited, corrected and extended by _Ray Chandler_, Jul 21 2011