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A282277 Numbers k such that (23*10^k + 97)/3 is prime. 0
3, 6, 11, 14, 20, 38, 55, 206, 1327, 1676, 1715, 1814, 2030, 2406, 2599, 3251, 4493, 5066, 6029, 8745, 24918, 26672, 70363, 77556 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For k>1, numbers such that the digit 7 followed by k-2 occurrences of the digit 6 followed by the digits 99 is prime (see Example section).

a(25) > 10^5.

LINKS

Table of n, a(n) for n=1..24.

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

Makoto Kamada, Search for 76w99.

EXAMPLE

6 is in this sequence because (23*10^6 + 97)/3 = 7666699 is prime.

Initial terms and primes associated:

a(1) = 3, 7699;

a(2) = 6, 7666699;

a(3) = 11, 766666666699;

a(4) = 14, 766666666666699;

a(5) = 20, 766666666666666666699; etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(23*10^# + 97)/3] &]

CROSSREFS

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

Sequence in context: A047924 A267519 A200182 * A122599 A015823 A049620

Adjacent sequences:  A282274 A282275 A282276 * A282278 A282279 A282280

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Feb 10 2017

STATUS

approved

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Last modified March 22 17:25 EDT 2019. Contains 321422 sequences. (Running on oeis4.)