A214290 Primes of the form XYYX, where Y is a single digit.

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

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