A198385 - OEIS

%I #28 Oct 19 2021 14:24:49

%S 25,100,169,225,289,400,625,676,625,841,900,1156,1369,1225,1681,1521,

%T 1600,2500,2025,2704,2601,2500,3721,2809,3025,4225,3364,3600,4225,

%U 4225,4225,4624,5625,5476,7225,4900,6724,6084,5329,5625,6400,7225,7225,7225,7921

%N Second of a triple of squares in arithmetic progression.

%H Ray Chandler, <a href="/A198385/b198385.txt">Table of n, a(n) for n = 1..10000</a>

%H Keith Conrad, <a href="http://www.math.uconn.edu/~kconrad/blurbs/ugradnumthy/3squarearithprog.pdf">Arithmetic progressions of three squares</a>

%H Reinhard Zumkeller, <a href="/A198384/a198384_2.txt">Table of initial values</a>

%F a(n) = A198389(n)^2.

%F a(n) - A198384(n) = A198386(n) - a(n) = A198387(n).

%F A198436(n) = a(A198409(n)).

%t wmax = 1000;

%t 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 Flatten[DeleteCases[triples /@ Range[wmax], {}], 2][[All, 2]] (* _Jean-François Alcover_, Oct 19 2021 *)

%o (Haskell)

%o a198385 n = a198385_list !! (n-1)

%o a198385_list = map (^ 2) a198389_list

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Oct 24 2011