A096498 Prime before n-th repunit.

7, 109, 1109, 11093, 111109, 1111091, 11111101, 111111109, 1111111097, 11111111059, 111111111103, 1111111111093, 11111111111053, 111111111111053, 1111111111111039, 11111111111111107, 111111111111111091, 1111111111111111037, 11111111111111111027, 111111111111111111053, 1111111111111111111097

Offset: 2

Author

Labos Elemer, Jul 09 2004

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 2..999

Crossrefs

Cf. A068693, A002275, A096497.

Programs

Maple

seq(prevprime((10^n-1)/9), n=2..50); # Robert Israel, Nov 13 2017

Mathematica

Table[NextPrime[(10^n - 1)/9, -1], {n, 2, 22}] (* updated by Michael De Vlieger, May 02 2016 *)

PARI

a(n) = precprime((10^n-1)/9 - 1); \\ Michel Marcus, May 02 2016

Formula

a(n) = A002275(n) - A096870(n) = A096497(n) - A096499(n).