A278471 - OEIS

A278471

Numbers k such that 10^k - 2001 is prime.

16, 18, 38, 82, 98, 318, 1106, 1914, 2438, 2640, 3156, 10330, 19278, 31976, 41140

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OFFSET

1,1

COMMENTS

For n>3, numbers such that n-4 occurrences of the digit 9 followed by the digits 7999 is prime.

LINKS

EXAMPLE

Initial terms and primes associated:

a(1) = 16, 9999999999997999;

a(2) = 18, 999999999999997999;

a(3) = 38, 99999999999999999999999999999999997999; etc.

MATHEMATICA

Select[Range[3, 10000], PrimeQ[10^# - 2001] &]

PROG

(Magma) [n: n in [3..700] | IsPrime(10^n-2001)];

(PARI) isok(n) = isprime(10^n - 2001); \\ Michel Marcus, Dec 03 2016

CROSSREFS

Cf. similar sequences listed in A278470.

KEYWORD

nonn,more

AUTHOR

EXTENSIONS

a(12) from Michael S. Branicky, Jan 29 2023

a(13) from Michael S. Branicky, Apr 10 2023

a(14)-a(15) from Kamada data by Tyler Busby, Apr 20 2024

STATUS

approved