A065685 Number of primes <= prime(n) which begin with a 6.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2

Offset

1,19

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Example

a(17) = 0, a(18) = 1: 61 = A000040(18) is the first prime beginning with 6. a(664579) = 72257 (A000040(664579) = 9999991 is the largest prime < 10^7).

Mathematica

Accumulate@ Array[Boole[First@ IntegerDigits@ Prime@ # == 6] &, 105] (* Michael De Vlieger, Jun 14 2018 *)

Prog

(PARI) lista(n) = { my(a=[p\10^logint(p, 10)==6 | p<-primes(n)]); for(i=2, #a, a[i]+=a[i-1]); a} \\ Harry J. Smith, Oct 26 2009

Crossrefs

Cf. A000040, A045712, A065680.

Sequence in context: A065687 A300403 A077433 * A084100 A329683 A130130

Adjacent sequences: A065682 A065683 A065684 * A065686 A065687 A065688

Keyword

base,nonn,changed

Author

Reinhard Zumkeller, Nov 13 2001

Status

approved