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A293910 Numbers k such that (26*10^k - 173)/3 is prime. 0
1, 2, 3, 8, 11, 13, 17, 28, 46, 67, 136, 536, 619, 746, 2420, 2672, 8228, 10861, 13424, 16047, 18075, 37720, 56371, 75055 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k>1, numbers such that the digit 8 followed by k-2 occurrences of the digit 6 followed by the digits 09 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 86w09

EXAMPLE

2 is in this sequence because (26*10^2 - 173)/3 = 809 is prime.

Initial terms and primes associated:

a(1) = 1, 29;

a(2) = 2, 809;

a(3) = 3, 8609;

a(4) = 8, 866666609;

a(5) = 11, 866666666609; etc.

MATHEMATICA

Select[Range[1, 100000], PrimeQ[(26*10^# - 173)/3] &]

CROSSREFS

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

Sequence in context: A201541 A084917 A134713 * A173269 A050557 A039000

Adjacent sequences:  A293907 A293908 A293909 * A293911 A293912 A293913

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Oct 19 2017

STATUS

approved

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Last modified April 20 08:37 EDT 2019. Contains 322306 sequences. (Running on oeis4.)