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A110674 Numbers k such that the string 1111k is prime. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A140118 A191106 A324699 * A003528 A032913 A261072

Adjacent sequences:  A110671 A110672 A110673 * A110675 A110676 A110677

KEYWORD

nonn,base

AUTHOR

Parthasarathy Nambi, Sep 14 2005

STATUS

approved

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Last modified September 24 04:08 EDT 2020. Contains 337316 sequences. (Running on oeis4.)