A165700 Numbers n such that n*10^(n+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

Links

Table of n, a(n) for n=1..6.

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

Cf. A068817, A084428.

Sequence in context: A207152 A135059 A203200 * A249635 A164135 A119056

Adjacent sequences: A165697 A165698 A165699 * A165701 A165702 A165703

Keyword

base,hard,more,nonn

Author

Farideh Firoozbakht, Sep 25 2009

Status

approved