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Primitive Pythagorean Quadruples a^2+b^2+c^2=d^2, 0<a<=b<=c<=d, gcd(a,b,c,d)=1, sorted by d, then c, then b; sequence gives c values.
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%I #8 May 24 2015 08:52:01

%S 2,6,7,8,7,9,12,11,14,12,12,15,17,18,16,16,19,20,18,18,22,16,20,22,23,

%T 23,25,26,21,24,24,21,22,27,30,20,25,28,28,31,32,32,26,30,30,33,27,28,

%U 28,36,26,29,29,34,34,35,24,31,32,33,39,30,30,38,39,42,42,29,35,37,40

%N Primitive Pythagorean Quadruples a^2+b^2+c^2=d^2, 0<a<=b<=c<=d, gcd(a,b,c,d)=1, sorted by d, then c, then b; sequence gives c values.

%H Ivan Neretin, <a href="/A096909/b096909.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PythagoreanQuadruple.html">Pythagorean Quadruple.</a>

%t mx = 50; res = {}; Do[If[GCD[b, c, d] > 1, Continue[]]; If[IntegerQ[a = Sqrt[d^2 - b^2 - c^2]] && a > 0 && a <= b, AppendTo[res, {a, b, c, d}]], {d, mx}, {c, d}, {b, c}]; res[[All, 3]] (* _Ivan Neretin_, May 24 2015 *)

%Y Cf. A096907, A096908, A096910.

%K nonn,look

%O 1,1

%A _Ray Chandler_, Aug 15 2004