A107644 Numbers n such that the string 1113n is the decimal expansion of a prime number.

1, 17, 23, 37, 41, 47, 73, 103, 137, 149, 157, 173, 181, 187, 193, 197, 199, 221, 239, 253, 257, 317, 319, 337, 349, 373, 379, 401, 403, 421, 451, 461, 481, 491, 509, 521, 527, 557, 569, 587, 599, 617, 643, 667, 701, 703, 713, 719, 751, 773, 781, 787, 793

Offset

1,2

Comments

11 and 13 are twin primes.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

n=1: 11131 is prime.
n=47: 111347 is prime.
n=149: 1113149 is prime.

Mathematica

Select[Range[800], PrimeQ[1113*10^IntegerLength[#]+#]&] (* Harvey P. Dale, Sep 26 2016 *)

Prog

(Magma) [ n: n in [1..800] | IsPrime(Seqint(Intseq(n) cat [3, 1, 1, 1])) ];

Crossrefs

Sequence in context: A080830 A165566 A072184 * A158710 A103805 A333327

Adjacent sequences: A107641 A107642 A107643 * A107645 A107646 A107647

Keyword

nonn,base

Author

Parthasarathy Nambi, Jun 09 2005

Status

approved