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A282138 Numbers k such that (19*10^k - 49)/3 is prime. 0
1, 2, 3, 4, 5, 6, 7, 21, 22, 101, 111, 132, 174, 201, 265, 335, 388, 537, 1011, 1012, 1254, 6766, 20236, 55833 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k>1, numbers such that the digit 6 followed by k-2 occurrences of the digit 3 followed by the digits 17 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 63w17.

EXAMPLE

3 is in this sequence because (19*10^3 - 49)/3 = 6317 is prime.

Initial terms and primes associated:

a(1) = 1, 47;

a(2) = 2, 617;

a(3) = 3, 6317;

a(4) = 4, 63317;

a(5) = 5, 633317; etc.

MATHEMATICA

Select[Range[1, 100000], PrimeQ[(19*10^# - 49)/3] &]

CROSSREFS

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

Sequence in context: A297182 A010354 A070759 * A106275 A031054 A153687

Adjacent sequences:  A282135 A282136 A282137 * A282139 A282140 A282141

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Feb 06 2017

STATUS

approved

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Last modified February 20 20:12 EST 2018. Contains 299385 sequences. (Running on oeis4.)