A091708 Number of primes less than 10^n having at least one digit 7.

1, 9, 68, 549, 4819, 43506, 397756, 3681943, 34344296, 322199867, 3036544958, 28722439343, 272501681533, 2591959274190

Offset: 1

Author

Enoch Haga, Jan 30 2004

Keywords

• nonn
• base

Examples

			a(1) = 1 because of the 4 primes less than 10^1, 1 has at least one digit 7.
		

Crossrefs

a(n) + A091641(n) = A006880(n).

Cf. A091644, A091645, A091646, A091647, A090705, A090706, A091707, A091709, A091710.

Programs

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], 7] != {}, c++ ]]; Print[c]; p--, {n, 1, 8}] (* Robert G. Wilson v, Feb 02 2004 *)
Table[Count[Prime[Range[PrimePi[10^n]]],?(DigitCount[#,10,7]>0&)],{n,12}] (* _Harvey P. Dale, Mar 03 2013 *)

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