login
Largest prime <= 3^n.
3

%I #10 Jun 20 2021 16:30:07

%S 3,7,23,79,241,727,2179,6553,19681,59029,177131,531383,1594301,

%T 4782961,14348891,43046623,129140153,387420479,1162261453,3486784393,

%U 10460353199,31381059607,94143178807,282429536453,847288609423

%N Largest prime <= 3^n.

%t PrimePrev[n_]:=Module[{k=n},While[ !PrimeQ[k],k-- ];k];f[n_]:=3^n;lst={};Do[AppendTo[lst,PrimePrev[f[n]]],{n,5!}];lst (* _Vladimir Joseph Stephan Orlovsky_, Feb 26 2010 *)

%t Join[{3},NextPrime[3^Range[2,50],-1]] (* _Harvey P. Dale_, Jun 20 2021 *)

%o (PARI) g(n,b) = for(x=0,n,print1(precprime(b^x)","))

%K easy,nonn

%O 1,1

%A _Cino Hilliard_, Mar 03 2005