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A129076 a(n) = sigma(sigma(sigma(sigma(n)))), where sigma(n) = sum of divisors of n.

%I A129076 #20 Sep 08 2022 08:45:30
%S A129076 1,8,15,24,56,120,60,168,60,120,120,360,168,480,480,104,120,360,252,
%T A129076 728,210,248,480,1512,104,728,546,1170,336,992,210,576,504,1170,504,
%U A129076 480,480,1512,1170,1344,728,1680,504,1560,1512,992,504,1560,384,432,992,588
%N A129076 a(n) = sigma(sigma(sigma(sigma(n)))), where sigma(n) = sum of divisors of n.
%C A129076 a(n) = A000203(A000203(A051027(n))) = A051027(A000203(A000203(n))) = A000203(A051027(A000203(n))) = A000203(A066971(n)) = A066971(A000203(n)) = A051027(A051027(n)). - _Jaroslav Krizek_, Jul 19 2009
%H A129076 Harvey P. Dale, <a href="/A129076/b129076.txt">Table of n, a(n) for n = 1..1000</a>
%F A129076 a(n) = A000203(A000203(A000203(A000203(n)))).
%t A129076 Nest[DivisorSigma[1,#]&,Range[60],4] (* _Harvey P. Dale_, Oct 05 2011 *)
%o A129076 (Magma) [ SumOfDivisors(SumOfDivisors(SumOfDivisors(SumOfDivisors(n)))) : n in [1..100]];
%o A129076 (PARI) a(n) = sigma(sigma(sigma(sigma(n)))); \\ _Michel Marcus_, Apr 29 2017
%Y A129076 Cf. A000203, A051027, A066971.
%Y A129076 Cf. A019293.
%K A129076 easy,nonn
%O A129076 1,2
%A A129076 _Jonathan Vos Post_, May 27 2007