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A214291 Primes of the form XYYYYYX, where Y is a single digit. 5

%I

%S 1333331,1444441,1777771,3222223,3444443,7666667,9222229,9888889,

%T 134444413,136666613,137777713,191111119,196666619,197777719,

%U 232222223,295555529,311111131,319999931,331111133,379999937,392222239,394444439

%N Primes of the form XYYYYYX, where Y is a single digit.

%H Vincenzo Librandi, <a href="/A214291/b214291.txt">Table of n, a(n) for n = 1..1000</a>

%t f[n_]:=Block[{len=Floor[Log[10,n]+1]},Select[10^(5+len) n+10^len*Table[k (10^5-1)/9,{k,9}]+n,PrimeQ@#&]];Array[f,3509]//Flatten

%o (MAGMA) m:=5; [p: d in [1..9], n in [1..50 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)]; // _Bruno Berselli_, Sep 12 2013

%Y Cf. A154270, A162423, A214290.

%K nonn,base

%O 1,1

%A _Vincenzo Librandi_, Jul 26 2012

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Last modified November 15 04:00 EST 2018. Contains 317225 sequences. (Running on oeis4.)