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A216449
Numbers k such that the first k digits of the string kkkk... correspond to a prime number.
0
15, 346, 1137, 1429, 11143, 21139
OFFSET
1,1
COMMENTS
The primality of the numbers corresponding to the first 4 terms has been certified with Primo.
EXAMPLE
k = 15 is in the sequence since the 15-digit number 151515151515151 is prime.
MATHEMATICA
f[n_]:=Block[{d=IntegerDigits@n}, FromDigits@d[[Mod[Range@n - 1, Length@d]+1]]]; Select[Range@1500, PrimeQ@f@# &]
CROSSREFS
Subsequence of A171491.
Sequence in context: A286391 A034975 A012787 * A030049 A240375 A202809
KEYWORD
nonn,base,more
AUTHOR
Giovanni Resta, Sep 11 2012
STATUS
approved