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A198385 Second of a triple of squares in arithmetic progression.

%I A198385 #28 Oct 19 2021 14:24:49
%S A198385 25,100,169,225,289,400,625,676,625,841,900,1156,1369,1225,1681,1521,
%T A198385 1600,2500,2025,2704,2601,2500,3721,2809,3025,4225,3364,3600,4225,
%U A198385 4225,4225,4624,5625,5476,7225,4900,6724,6084,5329,5625,6400,7225,7225,7225,7921
%N A198385 Second of a triple of squares in arithmetic progression.
%H A198385 Ray Chandler, <a href="/A198385/b198385.txt">Table of n, a(n) for n = 1..10000</a>
%H A198385 Keith Conrad, <a href="http://www.math.uconn.edu/~kconrad/blurbs/ugradnumthy/3squarearithprog.pdf">Arithmetic progressions of three squares</a>
%H A198385 Reinhard Zumkeller, <a href="/A198384/a198384_2.txt">Table of initial values</a>
%F A198385 a(n) = A198389(n)^2.
%F A198385 a(n) - A198384(n) = A198386(n) - a(n) = A198387(n).
%F A198385 A198436(n) = a(A198409(n)).
%t A198385 wmax = 1000;
%t A198385 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 A198385 Flatten[DeleteCases[triples /@ Range[wmax], {}], 2][[All, 2]] (* _Jean-François Alcover_, Oct 19 2021 *)
%o A198385 (Haskell)
%o A198385 a198385 n = a198385_list !! (n-1)
%o A198385 a198385_list = map (^ 2) a198389_list
%K A198385 nonn
%O A198385 1,1
%A A198385 _Reinhard Zumkeller_, Oct 24 2011