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%I #5 Dec 18 2018 11:11:26
%S 15,33,39,49,55,57,81,87,95,111,113,143,159,177,183,201,209,249,281,
%T 289,295,303,319,321,335,353,393,407,415,417,447,489,519,529,535,537,
%U 543,551,577,583,591,593,617,625,633,649,655,681,695,737,767,807,815,879,895,913,951
%N Odd numbers n for which A006694((n-1)/2)=4.
%C If p>3 is a prime then 3p is in this sequence if and only if p is in A001122.
%o (PARI) a006694(n)=sumdiv(2*n+1, d, eulerphi(d)/znorder(Mod(2, d))) - 1;
%o isok(n) = (n % 2) && (a006694((n-1)/2)== 4); \\ _Michel Marcus_, Dec 18 2018
%Y Cf. A006694, A001122, A001134.
%K nonn
%O 1,1
%A _Vladimir Shevelev_, Jun 16 2008
%E More terms from _Michel Marcus_, Dec 18 2018
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