

A110065


Numbers k such that 10^k  k is prime.


9




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^nn) \\ 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^nn).
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



