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Numbers k such that sigma(sigma(k)) == phi(k) (mod sigma(k)).
1

%I #14 Feb 11 2021 01:28:58

%S 2,26,77,85,194,335,707,1350,2443,2639,9158,9602,15238,16625,19698,

%T 23199,24416,52328,54663,56927,64206,67226,69875,82235,100837,104489,

%U 136213,150040,161268,230216,244572,251488,271215,273208,283492,298205,306878,352660

%N Numbers k such that sigma(sigma(k)) == phi(k) (mod sigma(k)).

%H Donovan Johnson, <a href="/A067204/b067204.txt">Table of n, a(n) for n = 1..500</a>

%o (PARI) for(n=1, 10^8, s=sigma(n); if(sigma(s)%s==eulerphi(n), print(n))) \\ _Donovan Johnson_, Feb 25 2013

%K nonn

%O 1,1

%A _Benoit Cloitre_, Feb 19 2002