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%I #10 May 11 2018 21:41:16
%S 4,8,9,16,18,20,25,36,45,49,50,64,72,80,100,104,116,117,121,128,144,
%T 148,169,180,196,200,208,225,234,242,244,256,261,289,292,296,320,325,
%U 333,361,369,404,436,441,450,452,464,488,512,529,548,549,576,578,584,592
%N Nonsquarefree numbers k such that sigma(k) is squarefree.
%H Robert Israel, <a href="/A086368/b086368.txt">Table of n, a(n) for n = 1..10000</a>
%e k = 45 = 3*3*5 and sigma(45) = 78 = 2*3*13.
%p filter:= n -> not numtheory:-issqrfree(n) and numtheory:-issqrfree(numtheory:-sigma(n)):
%p select(filter, [$1..1000]); # _Robert Israel_, May 11 2018
%Y Cf. A065303, A087249, A065301.
%K nonn
%O 1,1
%A _Labos Elemer_, Sep 05 2003
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