

A103967


Numbers n such that the string n1n is the decimal expansion of a prime number.


2



3, 9, 17, 21, 27, 29, 39, 41, 47, 51, 59, 71, 81, 87, 89, 113, 117, 119, 131, 137, 141, 159, 161, 177, 189, 201, 239, 263, 287, 291, 299, 333, 359, 371, 377, 389, 393, 399, 443, 459, 461, 467, 471, 489, 509, 539, 573, 603, 623, 653, 657, 659, 663, 671, 681
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OFFSET

1,1


COMMENTS

All terms are odd and not multiples of 5.  Zak Seidov, Oct 29 2014


LINKS

Zak Seidov, Table of n, a(n) for n = 1..10000


EXAMPLE

n=3 is in the sequence because n1n = 313 is prime.
n=41 is in the sequence because n1n = 41141 is prime.
n=89 is in the sequence because n1n = 89189 is prime.


MATHEMATICA

Reap[Do[If[Mod[n, 5]>0&&PrimeQ[ToExpression[ToString[n]<>"1"<>ToString[n]]], Sow[n]], {n, 3, 1000, 2}]][[2, 1]] (* Zak Seidov, Oct 29 2014 *)


PROG

(MAGMA) [ n: n in [0..800]  IsPrime(Seqint(Intseq(n) cat [1] cat Intseq(n))) ]; // Klaus Brockhaus, Feb 03 2011


CROSSREFS

Cf. A249374.
Sequence in context: A106676 A050795 A050797 * A032400 A329422 A004621
Adjacent sequences: A103964 A103965 A103966 * A103968 A103969 A103970


KEYWORD

base,nonn


AUTHOR

Parthasarathy Nambi, Mar 30 2005


STATUS

approved



