A147667 Primes of the form 5^k - 4^k.

61, 1136791005963704961126617632861, 173472015290681763212224222187425603741981, 31861838222649045530727106406255616308752331078816472270207782250106896363274089867800367051529351065966102374800998198276889145001421

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Nov 10 2008

Keywords

• nonn

Comments

All terms are odd, and if k is even, then 5^k - 4^k is divisible by 3. [Vincenzo Librandi, Nov 25 2010]

The next term (a(5)) has 156 digits. - Harvey P. Dale, May 14 2022

Examples

			5^3 - 4^3 = 125 - 64 = 61.
		

Links

• Muniru A Asiru, Table of n, a(n) for n = 1..9

Crossrefs

Cf. A059802 (corresponding n).

Programs

GAP

Filtered(List([1..200],n->5^n - 4^n),IsPrime); # Muniru A Asiru, Mar 04 2018

Maple

select(isprime, [seq(5^n - 4^n, n=0..200)]); # Muniru A Asiru, Mar 04 2018

Mathematica

lst={};Do[p=5^n-4^n;If[PrimeQ[p],AppendTo[lst,p]],{n,6!}];lst
Select[Table[5^n-4^n,{n,300}],PrimeQ] (* Harvey P. Dale, May 14 2022 *)