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A282340 Numbers k such that (184*10^k - 1)/3 is prime. 0
0, 1, 2, 3, 21, 24, 25, 39, 42, 90, 192, 547, 3185, 3363, 4279, 4496, 4761, 5022, 6807, 13220, 13283, 13519, 25183, 37609, 84348, 87473 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Numbers such that the digits 61 followed by k occurrences of the digit 3 is prime (see Example section).

a(27) > 10^5.

LINKS

Table of n, a(n) for n=1..26.

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

Makoto Kamada, Search for 613w.

EXAMPLE

2 is in this sequence because (184*10^2 - 1)/3 = 6133 is prime.

Initial terms and primes associated:

a(1) = 0, 61;

a(2) = 1, 613;

a(3) = 2, 6133;

a(4) = 3, 61333;

a(5) = 21, 61333333333333333333333; etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(184*10^# - 1)/3] &]

PROG

(PARI) isok(k) = isprime((184*10^k - 1)/3); \\ Michel Marcus, Feb 12 2017

CROSSREFS

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

Sequence in context: A124447 A250181 A024765 * A248953 A090122 A296254

Adjacent sequences:  A282337 A282338 A282339 * A282341 A282342 A282343

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Feb 12 2017

STATUS

approved

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Last modified August 25 04:05 EDT 2019. Contains 326318 sequences. (Running on oeis4.)