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%I #11 Dec 30 2024 03:17:56
%S 1,2,4,5,8,9,13,16,18,20,25,29,37,49,50,61,64,72,73,80,101,109,113,
%T 116,117,121,122,128,137,144,148,169,173,181,200,208,218,229,242,244,
%U 261,277,281,289,292,313,317,320,325,333,353,362,373,389,397,401,404,409
%N Numbers n such that both A000203(n) and A001157(n) are squarefree: sum of divisors and squares of divisors of n are squarefree.
%H Amiram Eldar, <a href="/A080403/b080403.txt">Table of n, a(n) for n = 1..10000</a>
%t Do[s1=MoebiusMu[DivisorSigma[1, n]]; s2=MoebiusMu[DivisorSigma[2, n]]; If[ !Equal[s1, 0]&&!Equal[s2, 0], Print[n]], {n, 1, 1000}]
%Y Cf. A001157, A000203, A065300, A080401, A080402.
%K easy,nonn
%O 1,2
%A _Labos Elemer_, Mar 19 2003