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A274914 Numbers k such that 88*10^k + 7 is prime. 0
1, 2, 3, 4, 8, 14, 17, 19, 24, 26, 30, 43, 81, 85, 171, 267, 282, 2384, 4201, 4450, 6995, 7170, 15049, 15681, 50547, 67691, 109022 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k>0, numbers such that the digits 88 followed by k-1 occurrences of the digit 0 followed by the digit 7 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 880w7.

EXAMPLE

4 is in this sequence because 88*10^4 + 7 = 880007is prime.

Initial terms and primes associated:

a(1) = 1, 887;

a(2) = 2, 8807;

a(3) = 3, 88007;

a(4) = 4, 880007;

a(5) = 8, 8800000007, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[88*10^# + 7] &]

PROG

(PARI) is(n)=ispseudoprime(88*10^n + 7) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

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

Sequence in context: A166342 A091816 A266400 * A100993 A117395 A006755

Adjacent sequences:  A274911 A274912 A274913 * A274915 A274916 A274917

KEYWORD

nonn,more

AUTHOR

Robert Price, Nov 11 2016

EXTENSIONS

a(27) from Robert Price, Mar 17 2020

STATUS

approved

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Last modified May 28 15:33 EDT 2020. Contains 334684 sequences. (Running on oeis4.)