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%I #18 Jun 12 2018 10:17:38
%S 1,7,11,13,19,23,29,31,37,41,43,47,49,53,59,61,67,71,73,77,79,83,89,
%T 91,97,101,103,107,109,113,121,127,131,133,137,139,143,149,151,157,
%U 161,163,167,169,173,179,181,191,193,197,199,203,209,211,217,223,227,229,233,239,241,247,251,253,259,263,269,271,277,281,283,287
%N Positive integers not divisible by any number of the form 2^n + 1 for n >= 0.
%C This is the same as odd numbers not divisible by numbers of the form 2^(2^i) + 1, i >= 0.
%C Asymptotically, the number of such numbers <= x is x/4 + o(x).
%C Composite terms are 49, 77, 91, 121, 133, 143, 161, ... - _Altug Alkan_, Sep 14 2017
%H Charles R Greathouse IV, <a href="/A292315/b292315.txt">Table of n, a(n) for n = 1..10000</a>
%t Position[Table[DivisorSum[n, 1 &, IntegerQ@ Log2[# - 1] &], {n, 288}], 0][[All, 1]] (* _Michael De Vlieger_, Jun 11 2018 *)
%o (PARI) list(lim)=my(v=List(),u=[],t); lim\=1; forstep(n=1,lim,[4,2], if(gcd(n,1431655765)==1, listput(v,n))); v=Vec(v); for(i=5,logint(logint(lim-1,2),2), t=2^2^i+1; u=concat(u,t*[1..lim\t])); u=Set(u); setminus(v,u) \\ _Charles R Greathouse IV_, Sep 14 2017
%Y Positions of zeros in A305436.
%K nonn
%O 1,2
%A _Jeffrey Shallit_, Sep 14 2017
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