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A216449 Numbers n such that the first n digits of the string nnnn... correspond to a prime number. 0

%I

%S 15,346,1137,1429,11143,21139

%N Numbers n such that the first n digits of the string nnnn... correspond to a prime number.

%C The primality of the numbers corresponding to the first 4 entries has been certified with Primo.

%e n=15 is in the sequence since the 15-digit number 151515151515151 is prime.

%t f[n_]:=Block[{d=IntegerDigits@n},FromDigits@d[[Mod[Range@n - 1,Length@d]+1]]]; Select[Range@1500,PrimeQ@f@# &]

%Y Subsequence of A171491.

%K nonn,base

%O 1,1

%A _Giovanni Resta_, Sep 11 2012

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Last modified April 3 01:23 EDT 2020. Contains 333195 sequences. (Running on oeis4.)