%I A070237
%S A070237 1,420,660,780,840,1320,1560,4620,5460,7140,7980,8580,9240,9660,10920,
%T A070237 11220,12012,12180,12540,13020,13260,14280,14820,15180,15540,15708,
%U A070237 15960,17160,17220,17556,17940,18060,18564,19140,19320,19380,19740
%N A070237 Numbers n such that the sign of core(n)-phi(n) is not equal to 2*mu(n)^2-1, 
               where core(x) is the square-free part of x.
%C A070237 Terms seem always congruent to 3. For almost k, sign(core(k)-phi(k))=2*mu(k)^2-1=2*A008683(k)-1.
%F A070237 a(n)=C*n + O(n), with C a constant conjectured to be a(2) = 420.
%o A070237 (PARI) for(n=1,25000,if(abs(sign(core(n)-eulerphi(n)-2*moebius(n)^2+1)>
               0,print1(n,",")))
%Y A070237 See A013929 for another interpretation.
%Y A070237 Sequence in context: A097822 A069064 A024410 this_sequence A156687 A147775 
               A135196
%Y A070237 Adjacent sequences: A070234 A070235 A070236 this_sequence A070238 A070239 
               A070240
%K A070237 easy,nonn
%O A070237 1,2
%A A070237 Benoit Cloitre (benoit7848c(AT)orange.fr), May 08 2002