A216449 Numbers k such that the first k digits of the string kkkk... correspond to a prime number.

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.

Links

Table of n, a(n) for n=1..6.

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

Adjacent sequences: A216446 A216447 A216448 * A216450 A216451 A216452

Keyword

nonn,base,more

Author

Giovanni Resta, Sep 11 2012

Status

approved