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A294231 Numbers k such that (56*10^k + 367)/9 is prime. 0
0, 1, 3, 6, 7, 12, 31, 33, 997, 1134, 3253, 3462, 6154, 9345, 10558, 13251, 15169, 18511, 19219, 22476, 25536, 31399, 35997, 51793, 124735 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

For k>1, numbers such that the digit 6 followed by k-2 occurrences of the digit 2 followed by the digits 63 is prime (see Example section).

a(26) > 2*10^5.

LINKS

Table of n, a(n) for n=1..25.

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

Makoto Kamada, Search for 62w63.

EXAMPLE

3 is in this sequence because (56*10^3 + 367)/9 = 6263 is prime.

Initial terms and primes associated:

a(1) = 0, 47;

a(2) = 1, 103;

a(3) = 3, 6263;

a(4) = 6, 6222263;

a(5) = 7, 62222263; etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(56*10^# + 367)/9] &]

CROSSREFS

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

Sequence in context: A333002 A333000 A175048 * A280873 A293437 A282354

Adjacent sequences:  A294228 A294229 A294230 * A294232 A294233 A294234

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Oct 25 2017

EXTENSIONS

a(25) from Robert Price, Jun 06 2019

STATUS

approved

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Last modified September 28 06:40 EDT 2021. Contains 347703 sequences. (Running on oeis4.)