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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
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).
Sequence in context: A212395 A027141 A002398 * A002816 A320265 A144479
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 April 20 10:09 EDT 2024. Contains 371812 sequences. (Running on oeis4.)