The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A091707 Number of primes less than 10^n having at least one digit 6. 10
 0, 2, 32, 332, 3225, 31792, 309431, 2991216, 28863327, 278085918, 2677289604, 25769815303, 248050788931, 2388172543971 (list; graph; refs; listen; history; text; internal format)
 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 8 18:48 EDT 2024. Contains 375023 sequences. (Running on oeis4.)