A138602 - OEIS

%I #4 Jun 13 2017 12:56:49

%S 20,21,22,23,32,33,83,140,1122

%N Numbers n such that 2^(2*n-39)-39 is prime.

%e 2^(2*23-39)-39=89, 2^(2*32-39)-39=33554393, 2^(2*33-39)-39=134217689, 2^(2*83-39)-39=170141183460469231731687303715884105689,

%t q=39;For[i=q,i<=q,a={};Do[x=2^(2*n-i)-i;If[PrimeQ[x],AppendTo[a,n]],{n,12^3}];Print["2^(2*n-",i,")-",i," ",a];i=i+2]

%o (PARI) is(n)=isprime(2^(2*n-39)-39) \\ _Charles R Greathouse IV_, Jun 13 2017

%K nonn,easy

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, May 13 2008