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

15, 346, 1137, 1429, 11143, 21139, 70776, 98328

Offset: 1

Author

Giovanni Resta, Sep 11 2012

Keywords

• nonn
• base
• more

Comments

The primality of the numbers corresponding to the first 4 terms has been certified with Primo.

Examples

			k = 15 is in the sequence since the 15-digit number 151515151515151 is prime.
		

Crossrefs

Subsequence of A171491.

Programs

Mathematica

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

Extensions

a(7)-a(8) from Michael S. Branicky, Dec 31 2024