A110674 Numbers k such that the string 1111k is prime.

3, 7, 9, 19, 21, 27, 43, 49, 87, 91, 151, 157, 169, 181, 183, 189, 211, 213, 219, 247, 259, 283, 289, 301, 333, 339, 351, 361, 379, 393, 399, 423, 427, 433, 447, 457, 489, 493, 499, 531, 543, 547, 553, 559, 573, 577, 637, 639, 651, 661, 667, 673, 687, 703, 711

Offset

1,1

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Example

If k=91 then 1111k = 111191 (prime).

Mathematica

Select[Range[720], PrimeQ[1111*10^IntegerLength[#] + #] &] (* Michael De Vlieger, Jan 22 2018 *)

Prog

(Magma) [ n: n in [1..1750] | IsPrime(Seqint(Intseq(n) cat [1, 1, 1, 1])) ]; // Vincenzo Librandi, Feb 02 2011

Crossrefs

Sequence in context: A396383 A191106 A324699 * A003528 A032913 A353397

Adjacent sequences: A110671 A110672 A110673 * A110675 A110676 A110677

Keyword

nonn,base

Author

Parthasarathy Nambi, Sep 14 2005

Status

approved