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A110065 Numbers k such that 10^k - k is prime. 9
3, 23, 171, 903, 9911, 48107, 48449, 60959 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For each n, a(n) == 3 (mod 6) or a(n) == 5 (mod 6).

There is no further term up to 16000. - Farideh Firoozbakht, Dec 02 2006

a(9) > 10^5. - Robert Price, Feb 19 2015

LINKS

Table of n, a(n) for n=1..8.

PROG

(PARI) is(n)=isprime(10^n-n) \\ Charles R Greathouse IV, Feb 17 2017

(Python)

from sympy import isprime

def afind(limit):

m, pow10 = 0, 1

while m <= limit:

if isprime(pow10 - m): print(m, end=", ")

m, pow10 = m + 1, pow10 * 10

afind(1000) # Michael S. Branicky, Mar 23 2021

CROSSREFS

Cf. A024115 (10^n-n).

Cf. A110066, A089379, A110067, A110068, A174175, A174176, A174177, A174178, A193881, A193882.

Sequence in context: A212395 A027141 A002398 * A002816 A320265 A144479

Adjacent sequences: A110062 A110063 A110064 * A110066 A110067 A110068

KEYWORD

more,nonn

AUTHOR

Farideh Firoozbakht, Jul 11 2005

EXTENSIONS

a(5) from Farideh Firoozbakht, Dec 02 2006

Definition corrected by Farideh Firoozbakht, Dec 12 2006

a(6)-a(8) from Robert Price, Feb 19 2015

STATUS

approved

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Last modified December 4 19:07 EST 2022. Contains 358563 sequences. (Running on oeis4.)