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A282620 Numbers k such that (67*10^k + 17)/3 is prime. 0
1, 2, 4, 8, 11, 20, 21, 32, 33, 41, 93, 187, 265, 380, 1088, 1459, 1671, 7328, 11524, 14167, 21719, 47439, 74045 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k>1, numbers such that the digits 22 followed by k-1 occurrences of the digit 3 followed by the digit 9 is prime (see Example section).

a(24) > 2*10^5.

LINKS

Table of n, a(n) for n=1..23.

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

Makoto Kamada, Search for 223w9.

EXAMPLE

4 is in this sequence because (67*10^4 + 17)/3 = 223339 is prime.

Initial terms and primes associated:

a(1) = 1, 229;

a(2) = 2, 2239;

a(3) = 4, 223339;

a(4) = 8, 2233333339;

a(5) = 11, 2233333333339; etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(67*10^# + 17)/3] &]

CROSSREFS

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

Sequence in context: A053439 A180379 A033956 * A320440 A288149 A159693

Adjacent sequences:  A282617 A282618 A282619 * A282621 A282622 A282623

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Feb 19 2017

STATUS

approved

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Last modified April 6 13:18 EDT 2020. Contains 333276 sequences. (Running on oeis4.)