OFFSET
1,2
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
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