Search: id:A154689
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%I A154689
%S A154689 5,7,10,13,14,18,19,26,31,38,39,43,50,55,61,62,69,72,73,78,84,86,91,95,
%T A154689 96,98,103,108,109,110,115,119,122,123,129,133,136,138,139,145,146,151,
%U A154689 153,159,181,182,187,190,193,199,205,206,209,213,217,218,219,221,229
%N A154689 Numbers n such that sigma_0(n-sigma_0(n))= sigma_0(n)
%C A154689 A000005(n-A00000(n)) = A000005(n). Primes in this sequence is A006512.
%D A154689 Jean-Marie De Koninck and Florian Luca: Positive Integers n Such That 
               sigma_0(phi(n)) = sigma_0(n), Journal of Integer Sequences, Vol. 
               11 (2008), Article 08.1.5.
%H A154689 J.-M. de Koninck, F. Luca, <a href="http://www.cs.uwaterloo.ca/journals/
               JIS/VOL11/DeKoninck/dekoninck47.html">Positive integers n such that 
               sigma(phi(n))=sigma(n)</a>, J. Int. Seq. vol 11 (2008), #08.1.5. 
               [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 15 2009]
%p A154689 A000005 := proc(n) numtheory[tau](n) ; end: for n from 1 to 1000 do a05 
               := A000005(n) ; if A000005(n-a05) = a05 then printf("%d,",n) ; fi; 
               od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 15 2009]
%Y A154689 Cf. A000005,A006512
%Y A154689 Sequence in context: A066513 A028810 A097700 this_sequence A024325 A060873 
               A112251
%Y A154689 Adjacent sequences: A154686 A154687 A154688 this_sequence A154690 A154691 
               A154692
%K A154689 easy,nonn
%O A154689 1,1
%A A154689 Ctibor O. Zizka (c.zizka(AT)email.cz), Jan 14 2009
%E A154689 Extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 15 2009

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