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A282809 Numbers k such that (82*10^k + 449)/9 is prime. 0
0, 3, 5, 6, 18, 21, 27, 36, 84, 95, 179, 492, 776, 1260, 4304, 5010, 5196, 7718, 15315, 20838, 20940, 24303, 26789, 72612, 157319 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k>1, numbers such that the digit 9 followed by k-2 occurrences of the digit 1 followed by the digits 61 is prime (see Example section).

a(26) > 2*10^5.

LINKS

Table of n, a(n) for n=1..25.

Makoto Kamada, Factorization of near-repdigit-related numbers.

Makoto Kamada, Search for 91w61.

EXAMPLE

5 is in this sequence because (82*10^5 + 449)/9 = 911161 is prime.

Initial terms and primes associated:

a(1) = 0, 59;

a(2) = 3, 9161;

a(3) = 5, 911161;

a(4) = 6, 9111161;

a(5) = 18, 9111111111111111161; etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(82*10^# + 449)/9] &] (* Corrected by Georg Fischer, Jul 22 2019 *)

CROSSREFS

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Sequence in context: A290761 A192119 A050563 * A168156 A295403 A272440

Adjacent sequences:  A282806 A282807 A282808 * A282810 A282811 A282812

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Feb 22 2017

EXTENSIONS

a(25) from Robert Price, Nov 09 2019

STATUS

approved

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Last modified December 7 05:14 EST 2019. Contains 329839 sequences. (Running on oeis4.)