A139781 - OEIS

%I #4 Aug 12 2012 11:54:39

%S 7,1031,25999,406898311,6357828601279,24253192047278040531416551,

%T 57824115865893569813730623892812790134879,

%U 22587545260114675708488599968932468124811638399,5514537417020184499142724613799550869468811634476741679

%N Primes of form (5^n - 2^n)/3.

%e (5^2-2^2)/3=7, (5^5-2^5)/3=1031, (5^7-2^7)/3=25999, ...

%t a={};Do[p=(5^n-2^n)/3;If[PrimeQ[p],AppendTo[a,p]],{n,20^2}];Print[a];

%t Select[Table[(5^n-2^n)/3,{n,0,500}],PrimeQ] (* _Harvey P. Dale_, Aug 12 2012 *)

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, May 16 2008

%E More terms from _Harvey P. Dale_, Aug 12 2012