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A198387 Common differences in triples of squares in arithmetic progression.

%I A198387 #21 Oct 21 2021 12:29:22
%S A198387 24,96,120,216,240,384,336,480,600,840,864,960,840,1176,720,1080,1536,
%T A198387 1344,1944,1920,2160,2400,1320,2520,2904,2016,3360,3456,3000,3696,
%U A198387 4056,3840,3024,3360,2184,4704,2880,4320,5280,5400,6144,5544,6000,6936,6240,5880
%N A198387 Common differences in triples of squares in arithmetic progression.
%H A198387 Ray Chandler, <a href="/A198387/b198387.txt">Table of n, a(n) for n = 1..10000</a>
%H A198387 Keith Conrad, <a href="http://www.math.uconn.edu/~kconrad/blurbs/ugradnumthy/3squarearithprog.pdf">Arithmetic progressions of three squares</a>
%H A198387 Reinhard Zumkeller, <a href="/A198384/a198384_1.txt">Table of initial values</a>
%F A198387 a(n) = A198385(n) - A198384(n) = A198386(n) - A198385(n).
%F A198387 A198438(n) = a(A198409(n)).
%t A198387 wmax = 1000;
%t A198387 triples[w_] := Reap[Module[{u, v}, For[u = 1, u < w, u++, If[IntegerQ[v = Sqrt[(u^2 + w^2)/2]], Sow[{u^2, v^2, w^2}]]]]][[2]];
%t A198387 #[[2]] - #[[1]]& /@ Flatten[DeleteCases[triples /@ Range[wmax], {}] , 2] (* _Jean-François Alcover_, Oct 21 2021 *)
%o A198387 (Haskell)
%o A198387 a198387 n = a198387_list !! (n-1)
%o A198387 a198387_list = zipWith (-) a198385_list a198384_list
%K A198387 nonn
%O A198387 1,1
%A A198387 _Reinhard Zumkeller_, Oct 24 2011