A214702 - OEIS

%I #12 Sep 08 2022 08:46:02

%S 100333331003,100388881003,100733331007,100766661007,100999991009,

%T 101333331013,101377771013,101755551017,102155551021,102722221027,

%U 102733331027,102922221029,102944441029,103133331031,103177771031,103199991031,103322221033,103366661033

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

%H Vincenzo Librandi, <a href="/A214702/b214702.txt">Table of n, a(n) for n = 1..1000</a>

%t f[n_]:=Block[{len=Floor[Log[10,n]+1]},Select[10^(4+len) n+10^len*Table[k (10^4-1)/9,{k,9}]+n,PrimeQ@#&]];Array[f,3509]//Flatten

%o (Magma) m:=4; [p: d in [1..9], n in [1..2000 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

%Y Cf. A154270, A162423, A214290, A214291.

%K nonn,base

%O 1,1

%A _Vincenzo Librandi_, Jul 27 2012