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A162880 Numbers k such that tau(sigma(k)) is not equal to sigma(tau(k)). 1

%I #5 Jun 25 2013 14:00:58

%S 2,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,

%T 28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,45,46,47,48,50,51,52,

%U 53,54,55,56,57,58,59,60,61,62,63,64,65,67,69,71,72,73,74,75,77,78,79,80

%N Numbers k such that tau(sigma(k)) is not equal to sigma(tau(k)).

%C The complement of A076361, that is, the indices k where A076360(k) is not zero.

%e a(6)= 8 is in the list because tau(sigma(8))=A062068(8)=4 whereas sigma(tau(8)) = A062069(8) = 7.

%o (PARI) is(n)=numdiv(sigma(n))!=sigma(numdiv(n)) \\ _Charles R Greathouse IV_, Jun 25 2013

%Y Cf. A000005, A000203, A076361, A076360.

%K nonn

%O 1,1

%A _Jaroslav Krizek_, Jul 16 2009

%E Edited by _R. J. Mathar_, Jul 21 2009

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Last modified March 28 11:59 EDT 2024. Contains 371254 sequences. (Running on oeis4.)