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A271618 Numbers k such that 10^k-801 is prime. 0
3, 4, 6, 14, 15, 16, 20, 46, 52, 114, 165, 468, 504, 568, 713, 748, 899, 958, 992, 1043, 1348, 2388, 3182, 4102, 8847, 10899, 11908, 18852, 25214, 40151, 40290, 51207, 71910, 166324 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For n>2, numbers such that n-3 occurrences of the digit 9 followed by the digits 199 is prime (see Example section).

a(35) > 2*10^5.

LINKS

Table of n, a(n) for n=1..34.

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

Makoto Kamada, Search for 9w199.

EXAMPLE

6 is in this sequence because 10^6-801 = 999199 is prime.

Initial terms and primes associated:

a(1) = 3, 199;

a(2) = 4, 9199;

a(3) = 6, 999199;

a(4) = 14, 99999999999199;

a(5) = 15, 999999999999199, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[10^#-801] &]

PROG

(PARI) is(n)=ispseudoprime(10^n-801) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

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

Sequence in context: A143100 A327584 A180859 * A137820 A049892 A063477

Adjacent sequences:  A271615 A271616 A271617 * A271619 A271620 A271621

KEYWORD

nonn,more

AUTHOR

Robert Price, Apr 11 2016

EXTENSIONS

a(34) from Robert Price, Feb 14 2018

STATUS

approved

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Last modified June 14 05:51 EDT 2021. Contains 345018 sequences. (Running on oeis4.)