A231596 Total number of 7's digits in primes less than 10^n.

1, 9, 78, 652, 6172, 58327, 560506, 5443074, 53152746, 521422184, 5132090751, 50642752951, 500714890907, 4958432528817

Offset

1,2

Links

Table of n, a(n) for n=1..14.

Example

a(2)=9, since there are 9 7's in primes less than 100. Namely: 7, 17, 37, 47, 67, 71, 73, 79, 97.

Mathematica

Table[Count[IntegerDigits[Prime[Range[PrimePi[10^n - 1]]]], 7, 2], {n, 7}] (* Robert Price, Jun 16 2019 *)

Crossrefs

Cf. A231411, A231590-A231598, A119290, A119291-A119300.

Sequence in context: A124131 A000445 A046196 * A350428 A190980 A254657

Adjacent sequences: A231593 A231594 A231595 * A231597 A231598 A231599

Keyword

more,nonn,base

Author

Robert Price, Nov 11 2013

Extensions

a(14) from Giovanni Resta, Jul 20 2015

Status

approved