A104094 Largest prime <= 9^n.

7, 79, 727, 6553, 59029, 531383, 4782961, 43046623, 387420479, 3486784393, 31381059607, 282429536453, 2541865828309, 22876792454939, 205891132094623, 1853020188851807, 16677181699666513, 150094635296999111

Offset: 1

Author

Cino Hilliard, Mar 03 2005

Keywords

• easy
• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..1046

Crossrefs

Cf. A013604.

Largest prime <= b^n: 2^n-A013603(n), 3^n-A013604(n), 4^n-A013606(n), 5^n-A013605(n), 6^n-A013607(n), 7^n-A013608(n), 8^n-A013603(3*n), 10^n-A033874(n).

Programs

Maple

f:= n -> prevprime(9^n):
map(f, [$1..30]); # Robert Israel, Aug 12 2019

Mathematica

NextPrime[#,-1]&/@(9^Range[20]) (* Harvey P. Dale, Apr 21 2024 *)

PARI

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

Formula

a(n) = 9^n - A013604(2*n) = A001019(n) - A013604(2*n), n > 0. A.H.M. Smeets, Aug 12 2019