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%I #7 Jul 15 2021 21:25:34
%S 1,15,560,570,1071,1102,1185,2035,2071,2128,2185,3007,3215,4087,4487,
%T 4584,5406,9204,10727,13912,16675,17951,17970,19127,20553,24288,24887,
%U 28247,28290,30216,34951,35807,35985,38551,40967,44472,44951,55247
%N Numbers k such that sigma(k) - phi(k) is a 4th power.
%H Harvey P. Dale, <a href="/A115918/b115918.txt">Table of n, a(n) for n = 1..340</a>
%e sigma(16675) - phi(16675) = 10000 = 10^4.
%t fpQ[n_]:=IntegerQ[(DivisorSigma[1,n]-EulerPhi[n])^(1/4)]; Select[Range[ 60000],fpQ] (* _Harvey P. Dale_, Jun 28 2012 *)
%Y Cf. A056917, A062385.
%K nonn
%O 1,2
%A _Giovanni Resta_, Feb 06 2006