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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 odd leg values.
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%I #3 Mar 30 2012 17:29:19

%S 1,3,7,1,7,9,3,11,5,9,1,15,17,1,11,13,19,5,13,3,3,15,9,7,23,23,25,7,

%T 21,11,3,21,21,27,5,17,25,7,17,31,7,1,15,17,1,33,27,21,3,3,19,29,29,

%U 13,19,35,23,31,9,33,39,25,7,9,39,7,9,29,35,37,13,19,5,27,21,27,11,21,43,23

%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 odd leg values.

%C One of a,b,c is odd, other two are even for primitive Pythagorean quadruples.

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

%Y Cf. A096907, A096908, A096909.

%K nonn

%O 1,2

%A _Ray Chandler_, Aug 15 2004