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Numbers k such that the string 10k is the decimal expansion of a prime number.
4

%I #14 Sep 08 2022 08:45:17

%S 1,3,7,9,13,19,21,31,33,39,49,51,61,63,69,87,91,93,97,103,111,133,139,

%T 141,151,159,163,169,177,181,193,211,223,243,247,253,259,267,271,273,

%U 289,301,303,313,321,331,333,337,343,357,369,391,399,427,429,433,453

%N Numbers k such that the string 10k is the decimal expansion of a prime number.

%H Daniel Starodubtsev, <a href="/A103601/b103601.txt">Table of n, a(n) for n = 1..10000</a>

%e 1 is in the sequence because 101 is prime.

%e 33 is in the sequence because 1033 is prime.

%e 141 is in the sequence because 10141 is prime.

%t A103601=Reap[For[n=1,n<10^3,If[PrimeQ[n+10^Floor[Log[10,100n]]],Sow[n]]; n+=2]][[2,1]] [From _Zak Seidov_, Dec 15 2008]

%o (Magma) [ n: n in [1..500] | IsPrime(Seqint(Intseq(n) cat [0, 1])) ];

%K base,nonn

%O 1,2

%A _Parthasarathy Nambi_, Mar 23 2005

%E More terms from _Zak Seidov_, Dec 15 2008