A154270 Primes of the form XYX, where Y is a single digit.

101, 131, 151, 181, 191, 313, 353, 373, 383, 727, 757, 787, 797, 919, 929, 11311, 11411, 13313, 13513, 13613, 13913, 17117, 17317, 17417, 19219, 19319, 19819, 19919, 21121, 21221, 21521, 21821, 23623, 27127, 27427, 27527, 27827, 29129

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Mathematica

Join[{101}, f[n_]:=Block[{len=Floor[Log[10, n]+1]}, Select[10^(1+len) n+10^len*Table[k (10^1-1)/9, {k, 9}]+n, PrimeQ@#&]]; Array[f, 40]//Flatten]; Vincenzo Librandi, Jul 27 2012
Select[Flatten[Table[FromDigits[Flatten[Join[{IntegerDigits[n], i, IntegerDigits[ n]}]]], {n, 50}, {i, 0, 9}]], PrimeQ] (* Harvey P. Dale, Aug 22 2014 *)

Prog

(Magma) [p: d in [0..9], n in [1..40 by 2] | IsPrime(p) where p is n*10^(t+1)+d*10^t+n where t is #Intseq(n)]; // Vincenzo Librandi, Sep 14 2013

Crossrefs

Cf. A162423, A214290, A214291.

Sequence in context: A075793 A319049 A052086 * A056730 A077798 A089360

Adjacent sequences: A154267 A154268 A154269 * A154271 A154272 A154273

Keyword

nonn,base

Author

Vincenzo Librandi, Jan 06 2009

Extensions

Inserted 19919. R. J. Mathar, Jan 07 2009

Status

approved