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%I #14 Mar 07 2021 03:17:35
%S 18,30,42,50,54,66,70,78,98,102,110,114,130,138,140,154,160,162,170,
%T 174,182,186,190,200,220,222,224,230,238,242,246,250,258,260,266,282,
%U 286,290,308,310,315,318,322,338,340,350,352,354,364,366,370,374,380,392
%N Those positive integers k where both d(d(k)) is not coprime to k and d(d(k)) does not divide k, where d(k) is the number of divisors of k.
%H Amiram Eldar, <a href="/A141115/b141115.txt">Table of n, a(n) for n = 1..10000</a>
%e 50 has 6 divisors and 6 has 4 divisors. 4 is not coprime to 50 and 4 does not divide 50. So 50 is in the sequence.
%t Select[Range[400], GCD[DivisorSigma[0,DivisorSigma[0, # ]], # ] > 1 && Mod[ #, DivisorSigma[0, DivisorSigma[0, # ]]] > 0 &] (* _Stefan Steinerberger_, Jun 05 2008 *)
%Y Cf. A010553, A141113, A141114.
%K nonn
%O 1,1
%A _Leroy Quet_, Jun 04 2008
%E More terms from _Stefan Steinerberger_, Jun 05 2008
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