A178434 Numbers n such that 10^n - 71 is prime.

2, 3, 4, 5, 7, 9, 10, 14, 22, 98, 127, 151, 158, 274, 377, 1015, 2146, 8499, 13885, 13991, 17834, 18211, 36271, 52317, 53804, 104212, 117059, 178695

Offset: 1

Author

Robert Price, Dec 21 2010

Keywords

• more
• nonn

Comments

a(29) > 2.5*10^5. - Robert Price, Apr 12 2015

Examples

			10^4 - 71 = 9929 which is a prime number.
		

Links

• Makoto Kamada, Near-repdigit numbers of the form AA...AABA.
• Makoto Kamada, Prime numbers of the form 99...9929.
• Index entries for primes involving repunits.

Crossrefs

Cf. A108330, A108328.

Programs

Mathematica

nMax=1000; Do[If[PrimeQ[10^n-71], Print[n]], {n, nMax}]

PARI

is(n)=ispseudoprime(10^n-71) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(24:25)=52317,53804 from Robert Price, Apr 25 2011

a(26)-a(28) from Kamada data by Robert Price, Apr 12 2015