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%I #14 Jul 15 2021 06:34:49
%S 3,81,400,972,1209,1276,1480,1833,2700,3408,4080,4345,6321,6498,6885,
%T 8673,8697,10257,12325,13192,13240,13409,14496,14560,16932,17232,
%U 18168,18904,19140,19344,20196,22896,23568,23920,27001,27313,28305
%N Numbers k such that k + sigma(k) + phi(k) is a square.
%H Amiram Eldar, <a href="/A116009/b116009.txt">Table of n, a(n) for n = 1..10000</a>
%e 81 + sigma(81) + phi(81) = 16^2.
%t Select[Range[30000], IntegerQ@Sqrt[# +DivisorSigma[1, #]+EulerPhi[#]] &] (* _Amiram Eldar_, Aug 13 2019 *)
%o (PARI) isok(n) = issquare (n + sigma(n) + eulerphi(n)); \\ _Michel Marcus_, Jan 26 2014
%Y Cf. A116007, A116008.
%K nonn
%O 1,1
%A _Giovanni Resta_, Feb 13 2006
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