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%I #12 Oct 27 2023 22:00:46
%S 2,3,4,5,7,8,11,12,13,14,17,18,19,23,24,26,27,29,31,32,35,37,38,40,41,
%T 43,47,52,53,56,59,61,62,63,65,66,67,71,73,74,77,79,83,86,88,89,90,92,
%U 95,97,101,103,104,107,109,110,112,113,119,122,125,127,128,131,134,136
%N Numbers n such that Chowla's function of n is divisible by the number of proper divisors of n.
%C Chowla's function (A048050) = sum of divisors of n except 1 and n.
%H Amiram Eldar, <a href="/A054021/b054021.txt">Table of n, a(n) for n = 1..10000</a>
%p with(numtheory):
%p [seq(`if`((sigma(i)-i-1) mod (tau(i)-1)=0,i,print( )),i=2..1000)];
%t Select[Range[2,150],Divisible[DivisorSigma[1,#]-1-#,DivisorSigma[ 0,#]-1]&] (* _Harvey P. Dale_, Aug 13 2018 *)
%Y Complement is A054020.
%Y Cf. A032741, A048050, A054015.
%K nonn
%O 1,1
%A _Asher Auel_, Jan 19 2000
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