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A195879 Positive integers a for which there is a (1/2)-Pythagorean triple (a,b,c) satisfying a<=b.

%I A195879 #8 Mar 30 2012 18:57:48
%S A195879 2,3,4,5,6,6,7,7,8,9,10,10,10,11,11,12,12,13,13,14,14,14,14,15,15,15,
%T A195879 16,16,17,17,18,18,18,18,19,19,20,20,20,21,21,21,21,22,22,22,22,23,24,
%U A195879 24,25,25,26,26,26,26,26,27,27,28,28,28,28,29,29,30,30,30,30,31
%N A195879 Positive integers a for which there is a (1/2)-Pythagorean triple (a,b,c) satisfying a<=b.
%C A195879 See A195770 for definitions of k-Pythagorean triple, primitive k-Pythagorean triple, and lists of related sequences.
%t A195879 z8 = 800; z9 = 400; z7 = 100;
%t A195879 k = 1/2; c[a_, b_] := Sqrt[a^2 + b^2 + k*a*b];
%t A195879 d[a_, b_] := If[IntegerQ[c[a, b]], {a, b, c[a, b]}, 0]
%t A195879 t[a_] := Table[d[a, b], {b, a, z8}]
%t A195879 u[n_] := Delete[t[n], Position[t[n], 0]]
%t A195879 Table[u[n], {n, 1, 15}]
%t A195879 t = Table[u[n], {n, 1, z8}];
%t A195879 Flatten[Position[t, {}]]
%t A195879 u = Flatten[Delete[t, Position[t, {}]]];
%t A195879 x[n_] := u[[3 n - 2]];
%t A195879 Table[x[n], {n, 1, z7}]  (* A195879 *)
%t A195879 y[n_] := u[[3 n - 1]];
%t A195879 Table[y[n], {n, 1, z7}]  (* A195880 *)
%t A195879 z[n_] := u[[3 n]];
%t A195879 Table[z[n], {n, 1, z7}]  (* A195881 *)
%t A195879 x1[n_] := If[GCD[x[n], y[n], z[n]] == 1, x[n], 0]
%t A195879 y1[n_] := If[GCD[x[n], y[n], z[n]] == 1, y[n], 0]
%t A195879 z1[n_] := If[GCD[x[n], y[n], z[n]] == 1, z[n], 0]
%t A195879 f = Table[x1[n], {n, 1, z9}];
%t A195879 x2 = Delete[f, Position[f, 0]]  (* A195882 *)
%t A195879 g = Table[y1[n], {n, 1, z9}];
%t A195879 y2 = Delete[g, Position[g, 0]]  (* A195883 *)
%t A195879 h = Table[z1[n], {n, 1, z9}];
%t A195879 z2 = Delete[h, Position[h, 0]]  (* A195884 *)
%Y A195879 Cf. A195770, A195880, A195882.
%K A195879 nonn
%O A195879 1,1
%A A195879 _Clark Kimberling_, Sep 25 2011