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A275096 Numbers n such that 2*10^n + 89 is prime. 0
1, 3, 4, 8, 9, 10, 13, 20, 27, 74, 89, 93, 137, 139, 296, 310, 662, 749, 1249, 2540, 2848, 3309, 8677, 11573, 15286, 17125, 39526, 42187, 44476, 47823, 92897 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For n>1, numbers n such that the digit 2 followed by n-2 occurrences of the digit 0 followed by the digits 89 is prime (see Example section).

a(32) > 10^5.

LINKS

Table of n, a(n) for n=1..31.

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

Makoto Kamada, Search for 20w89.

EXAMPLE

3 is in this sequence because 2*10^3 + 89 = 2089 is prime.

Initial terms and associated primes:

a(1) = 1, 109;

a(2) = 3, 2089;

a(3) = 4, 20089;

a(4) = 8, 200000089;

a(5) = 9, 2000000089, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[2*10^# + 89] &]

PROG

(MAGMA) [n: n in [1..500] | IsPrime(2*10^n+89)]; // Vincenzo Librandi, Jul 17 2016

(PARI) is(n)=ispseudoprime(2*10^n+89) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

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

Sequence in context: A296497 A019811 A075746 * A109826 A228145 A243064

Adjacent sequences:  A275093 A275094 A275095 * A275097 A275098 A275099

KEYWORD

nonn,more

AUTHOR

Robert Price, Jul 16 2016

STATUS

approved

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Last modified January 26 01:48 EST 2020. Contains 331270 sequences. (Running on oeis4.)