A138581 - OEIS

%I #8 Jul 11 2023 11:20:12

%S 8,9,10,11,19,55,125,953

%N Numbers n such that 2^(2*n-15)-15 is prime.

%e 2^(2*11-15)-15=113, 2^(2*19-15)-15=8388593, 2^(2*55-15)-15=39614081257132168796771975153, ...

%t q=15;For[i=q,i<=q,a={};Do[x=2^(2*n-i)-i;If[PrimeQ[x],AppendTo[a,n]],{n,10^2}];Print["2^(2*n-",i,")-",i," ",a];i=i+2]

%t Select[Range[1000],PrimeQ[2^(2#-15)-15]&] (* _Harvey P. Dale_, Jul 11 2023 *)

%o (PARI) is(n)=isprime(2^(2*n-15)-15) \\ _Charles R Greathouse IV_, Jun 13 2017

%K nonn,easy

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, May 13 2008

%E One more term (a(8)) from _Harvey P. Dale_, Jul 11 2023