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A280584 Numbers k such that (14*10^k - 83)/3 is prime. 0
1, 2, 3, 4, 6, 10, 11, 24, 53, 83, 97, 156, 157, 162, 182, 233, 355, 499, 629, 1252, 6378, 8366, 26406, 35345, 107694, 126784, 195234 (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 39 is prime (see Example section).

a(28) > 2*10^5.

LINKS

Table of n, a(n) for n=1..27.

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

Makoto Kamada, Search for 46w39.

EXAMPLE

4 is in this sequence because (14*10^4 - 83) / 3 = 46639 is prime.

Initial terms and primes associated:

a(1) = 1, 19;

a(2) = 2, 439;

a(3) = 3, 4639;

a(4) = 4, 46639;

a(5) = 6, 4666639; etc.

MATHEMATICA

Select[Range[1, 100000], PrimeQ[(14*10^# - 83) / 3] &]

PROG

(PARI) is(n)=ispseudoprime((14*10^n - 83)/3) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

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

Sequence in context: A005453 A180242 A187966 * A225649 A225651 A191149

Adjacent sequences:  A280581 A280582 A280583 * A280585 A280586 A280587

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Jan 05 2017

EXTENSIONS

a(25)-a(27) from Robert Price, Dec 23 2018

STATUS

approved

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Last modified July 5 21:00 EDT 2020. Contains 335473 sequences. (Running on oeis4.)