A091705 Number of primes less than 10^n having at least one digit 4.

0, 3, 32, 326, 3231, 31953, 310456, 3000349, 28922364, 278508004, 2680391313, 25793058269, 248228108241, 2389543008906

Offset: 1

Author

Enoch Haga, Jan 30 2004

Keywords

• nonn
• base

Examples

			a(2) = 3 because of the 25 primes less than 10^2, 3 have at least one digit 4.
		

Crossrefs

a(n) + A091638(n) = A006880(n).

Cf. A091644, A091645, A091646, A091647, A091706, A091707, A091708, 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], 4] != {}, c++ ]]; Print[c]; p--, {n, 1, 8}] (* Robert G. Wilson v, Feb 02 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