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%I #16 Apr 10 2013 17:32:05
%S 9,16,36,278784,251381025,2390623236,240055902025,354328515025,
%T 1022960302225,1298266542225,6824670333649,9433221536025,
%U 16614933604164,33314541015625,474897452948164,500279020818724,1387202986290276,2162188899431649,16053088159411524
%N Square numbers n for which sigma(n) + d(n) is also a perfect square.
%e 16 is in the list since 16 = 4^2 and sigma(16)+d(16) = 36 = 6^2. Also 278784 = 528^2 and sigma(278784)+d(278784) = 883600 = 940^2.
%t Sqd[n_] := Sqrt[DivisorSigma[1, n] + DivisorSigma[0, n]]; t = {}; Do[If[IntegerQ[Sqd[n^2]], AppendTo[t, n^2]], {n, 1500000}];t
%Y Cf. A007503.
%K nonn
%O 1,1
%A _Jayanta Basu_, Apr 10 2013
%E a(11)-a(19) from _Donovan Johnson_, Apr 10 2013