A091707 Number of primes less than 10^n having at least one digit 6.

0, 2, 32, 332, 3225, 31792, 309431, 2991216, 28863327, 278085918, 2677289604, 25769815303, 248050788931, 2388172543971

Offset

1,2

Links

Table of n, a(n) for n=1..14.

Example

a(1) = 0 because of the 4 primes less than 10^1, none have at least one digit 6.

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], 6] != {}, c++ ]]; Print[c]; p--, {n, 1, 8}] (* Robert G. Wilson v, Feb 02 2004 *)

Prog

(Python)
from sympy import sieve # use slower primerange for larger terms
def a(n): return sum('6' in str(p) for p in sieve.primerange(2, 10**n))
print([a(n) for n in range(1, 8)]) # Michael S. Branicky, Apr 23 2021

Crossrefs

a(n) + A091640(n) = A006880(n).

Cf. A091644, A091645, A091646, A091647, A091705, A091706, A091708, A091709, A091710.

Sequence in context: A079766 A224293 A053065 * A323639 A060868 A350138

Adjacent sequences: A091704 A091705 A091706 * A091708 A091709 A091710

Keyword

nonn,base

Author

Enoch Haga, Jan 30 2004

Extensions

Edited and extended by Robert G. Wilson v, Feb 02 2004

3 more terms from Ryan Propper, Aug 21 2005

a(13) from Robert Price, Nov 11 2013

a(14) from Giovanni Resta, Jul 21 2015

Status

approved