OFFSET
1,1
COMMENTS
Number of primes less than 10^n after removing any primes with at least one digit 3.
EXAMPLE
a(2)=16 because there are 25 primes less than 10^2, 9 have at least one digit 3; 25-9 = 16.
MATHEMATICA
NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; c = 0; p = 1; Do[ While[ p = NextPrim[p]; p < 10^n, If[ Position[ IntegerDigits[p], 3] == {}, c++ ]]; Print[c]; p--, {n, 1, 8}] (* Robert G. Wilson v, Feb 02 2004 *)
Table[Count[Prime[Range[PrimePi[10^n]]], _?(DigitCount[#, 10, 3]==0&)], {n, 8}] (* Harvey P. Dale, Oct 04 2011 *)
PROG
(PARI) good(n)=n=eval(Vec(Str(n))); for(i=1, #n, if(n[i]==3, return(1))); 0
a(n)=my(s); forprime(p=2, 10^n, s+=good(p)); s \\ Charles R Greathouse IV, Oct 04 2011
(Python)
from sympy import primerange
def a(n): return sum('3' not in str(p) for p in primerange(2, 10**n))
print([a(n) for n in range(1, 7)]) # Michael S. Branicky, Mar 16 2021
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Enoch Haga, Jan 30 2004
EXTENSIONS
Edited and extended by Robert G. Wilson v, Feb 02 2004
a(9)-a(12) from Donovan Johnson, Feb 14 2008
a(13) from Robert Price, Nov 08 2013
a(14) from Giovanni Resta, Mar 20 2017
STATUS
approved