The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A091640 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A091640

Number of primes less than 10^n which do not contain the digit 6.
(history; published version)

#17 by Michel Marcus at Fri Apr 23 11:55:51 EDT 2021

STATUS

reviewed

approved

#16 by Joerg Arndt at Fri Apr 23 10:21:02 EDT 2021

STATUS

proposed

reviewed

#15 by Michael S. Branicky at Fri Apr 23 09:48:09 EDT 2021

STATUS

editing

proposed

#14 by Michael S. Branicky at Fri Apr 23 09:30:26 EDT 2021

PROG

(Python)

from sympy import sieve # use slower primerange for larger terms

def a(n): return sum('6' not 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

STATUS

approved

editing

#13 by Giovanni Resta at Mon Mar 20 05:43:32 EDT 2017

STATUS

editing

approved

#12 by Giovanni Resta at Mon Mar 20 04:41:35 EDT 2017

DATA

4, 23, 136, 897, 6367, 46706, 355148, 2770239, 21984207, 176966593, 1440765209, 11838096715, 98014747908, 816769206831

EXTENSIONS

a(14) from Giovanni Resta, Mar 20 2017

STATUS

approved

editing

#11 by T. D. Noe at Fri Nov 08 16:38:42 EST 2013

STATUS

editing

approved

#10 by T. D. Noe at Fri Nov 08 16:38:40 EST 2013

FORMULA

a(n) = A006880(n) - A091707(n).

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}] (from * _Robert G. Wilson v _, Feb 02 2004 *)

CROSSREFS

a(n) + A091707(n) = A006880(n).

STATUS

proposed

editing

#9 by Robert Price at Fri Nov 08 14:59:11 EST 2013

STATUS

editing

proposed

#8 by Robert Price at Fri Nov 08 14:57:12 EST 2013

DATA

4, 23, 136, 897, 6367, 46706, 355148, 2770239, 21984207, 176966593, 1440765209, 11838096715, 98014747908

EXTENSIONS

a(13) from Robert Price, Nov 08 2013

STATUS

approved

editing