login
A228421
Count of the first 10^n primes which do not contain the digit 9.
20
1, 8, 69, 620, 5010, 45732, 418142, 3785060, 32579606, 296601070, 2683254222, 24354108057, 212324183352
OFFSET
0,2
FORMULA
a(n) <= 9^n. - Charles R Greathouse IV, May 21 2014
EXAMPLE
a(1) = 8 since there are 8 primes in the first 10 (through 29) that do not contain a 9. Namely: 2, 3, 5, 7, 11, 13, 17, 23.
MATHEMATICA
Table[Length[Select[Range[10^n], DigitCount[Prime[#], 10, 9] == 0 &]], {n, 0, 5}] (* Robert Price, Mar 23 2020 *)
PROG
(Python)
def a(n):
count = 0
for k in range(1, 10**n+1):
if '9' not in str(prime(k)):
count += 1
return count
n = 0
while n < 10:
print(a(n), end=', ')
n += 1
# Derek Orr, Jul 27 2014
KEYWORD
more,nonn,base,hard
AUTHOR
Robert Price, Nov 09 2013
EXTENSIONS
a(12) from Lucas A. Brown, Mar 19 2024
STATUS
approved