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%I #6 Feb 11 2014 19:05:22
%S 1,95,99,146,323,377,1095,1102,1351,1368,1630,1919,1943,2261,2639,
%T 2743,3915,4607,4743,5042,5045,5183,5249,6347,6497,7389,8265,8307,
%U 8749,9407,9701,10877,12535,13184,13253,14344,14535,16965,18405,19493,19836
%N Numbers n such that sigma(n)^2 - phi(n)^2 is a perfect square.
%H Donovan Johnson, <a href="/A057654/b057654.txt">Table of n, a(n) for n = 1..1000</a>
%e sigma(95)^2 - phi(95)^2 = 120^2 - 72^2 = 96^2, so 95 is a term of the sequence.
%t Select[Range[10^4], IntegerQ[Sqrt[DivisorSigma[1, # ]^2 - EulerPhi[ # ]^2]] &]
%K easy,nonn
%O 1,2
%A _Joseph L. Pe_, Feb 12 2002
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