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A284886 Numbers k such that (14*10^k-101)/3 is prime. 0
1, 2, 4, 6, 14, 20, 305, 470, 507, 1104, 1152, 1725, 1944, 5864, 6785, 7446, 11460, 12412, 16302, 19787, 24029, 27240, 67235, 83471, 89480, 116112 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k>1, numbers such that the digit 4 followed by k-2 occurrences of the digit 6 followed by the digits 33 is prime (see Example section).

a(27) > 2*10^5.

LINKS

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

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

Makoto Kamada, Search for 46w33.

EXAMPLE

4 is in this sequence because (14*10^4 - 101)/3 = 46633 is prime.

Initial terms and primes associated:

a(1) = 1, 13;

a(2) = 2, 433;

a(3) = 4, 46633;

a(4) = 6, 4666633;

a(5) = 14, 466666666666633; etc.

MATHEMATICA

Select[Range[1, 100000], PrimeQ[(14*10^# - 101)/3] &]

CROSSREFS

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

Sequence in context: A032353 A062112 A226302 * A249339 A307676 A084685

Adjacent sequences:  A284883 A284884 A284885 * A284887 A284888 A284889

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Apr 04 2017

EXTENSIONS

a(26) from Robert Price, Feb 23 2019

STATUS

approved

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Last modified October 14 09:57 EDT 2019. Contains 327995 sequences. (Running on oeis4.)