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A214290 Primes of the form XYYX, where Y is a single digit. 6
131113, 137713, 172217, 178817, 179917, 191119, 215521, 233323, 235523, 271127, 272227, 278827, 293329, 313331, 317731, 319931, 377737, 392239, 437743, 472247, 476647, 491149, 511151, 512251, 533353, 571157, 575557, 577757, 578857, 599959, 617761, 635563, 677767 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

MATHEMATICA

f[n_]:=Block[{len=Floor[Log[10, n]+1]}, Select[10^(2+len) n+10^len*Table[k (10^2-1)/9, {k, 9}]+n, PrimeQ@#&]]; Array[f, 1009]//Flatten

Select[Flatten[Table[FromDigits[Join[IntegerDigits[n], PadRight[{}, 2, i], IntegerDigits[ n]]], {n, 70}, {i, 9}]], PrimeQ] (* Harvey P. Dale, Jan 27 2015 *)

PROG

(MAGMA) m:=2; [p: d in [1..9], n in [1..70 by 2] | IsPrime(p) where p is n*(10^(m+t)+1)+d*10^t*(10^m-1) div 9 where t is #Intseq(n)]; // Vincenzo Librandi, Sep 14 2013

CROSSREFS

Cf. A154270, A162423.

Sequence in context: A017697 A013965 A036095 * A187939 A234687 A170782

Adjacent sequences:  A214287 A214288 A214289 * A214291 A214292 A214293

KEYWORD

nonn,base

AUTHOR

Vincenzo Librandi, Jul 26 2012

STATUS

approved

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Last modified October 20 01:39 EDT 2018. Contains 316378 sequences. (Running on oeis4.)