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A165700

Numbers k such that k*10^(k+1) + 1 is prime.

1, 7, 39, 1203, 10723, 11971

OFFSET

1,2

COMMENTS

Numbers n such that the number that begins with n, followed by n zeros, ends with 1 is prime.

Those numbers corresponding to a(4), a(5) and a(6) are probable primes.

There is no further term up to 14000.

There is no further term up to 30000. - Michael S. Branicky, Mar 22 2023

There is no further term up to 50000. - Michael S. Branicky, Oct 13 2024

LINKS

MATHEMATICA

Do[If[PrimeQ[n*10^(n+1)+1], Print[n]], {n, 14000}]

PROG

(PARI) is(n)=isprime(n*10^(n+1)+1) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

KEYWORD

base,hard,more,nonn

AUTHOR

STATUS

approved

URL: https://oeis.org/A165700