A234422 Number of primes <= 123...n.

0, 5, 30, 202, 1474, 11601, 95360, 809227, 7027260, 556442057, 46063874346, 3930144647471, 342720306370180, 30384643585371049, 2728974793135786013, 247673123284120245960, 22671892206713857205404

Offset

1,2

Links

Table of n, a(n) for n=1..17.

Formula

a(n) = A000720(A007908(n)).

Example

There are 1474 primes <= 12345 so a(5) = 1474.

Mathematica

PrimePi[Table[FromDigits[Flatten[IntegerDigits[Range[n]]]], {n, 12}]] (* Alonso del Arte, Dec 25 2013 *)

Prog

(Python)
def Num(x):
..num = ''
..for n in range(x):
....num += str(n+1)
..return num
from sympy import primepi
x = 1
while x < 10:
..print(primepi(int(Num(x))), end=', ')
..x += 1
# Edited by Derek Orr, Apr 05 2015
(PARI) s=""; for(n=1, 20, s=concat(s, n); print1(primepi(eval(s)), ", ")) \\ Derek Orr, Apr 05 2015

Crossrefs

Cf. A007908, A000720.

Sequence in context: A128328 A245376 A118346 * A091927 A253076 A165312

Adjacent sequences: A234419 A234420 A234421 * A234423 A234424 A234425

Keyword

nonn,base,hard,more

Author

Derek Orr, Dec 25 2013

Extensions

a(11)-a(12) from Donovan Johnson, Dec 29 2013

a(13)-a(16) from Chai Wah Wu, May 18 2020

a(17) from Chai Wah Wu, May 20 2020

Status

approved