login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A234422 Number of primes <= 123...n. 0
0, 5, 30, 202, 1474, 11601, 95360, 809227, 7027260, 556442057, 46063874346, 3930144647471, 342720306370180, 30384643585371049, 2728974793135786013, 247673123284120245960, 22671892206713857205404 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 28 08:33 EDT 2020. Contains 337394 sequences. (Running on oeis4.)