OFFSET
0,2
COMMENTS
A good approximation seems to be ceiling(log(10^n)*log(6*10^n)/(log(3)*log(4))). - Horst H. Manninger, Oct 29 2022
LINKS
David A. Corneth, Table of n, a(n) for n = 0..1999
FORMULA
a(n) = A071521(10^n). - Chai Wah Wu, Oct 23 2024
EXAMPLE
a(1) = 7 as there are 7 3-smooth numbers less than 10^1 = 10; they are 1, 2, 3, 4, 6, 8, 9. - David A. Corneth, Nov 14 2019
MATHEMATICA
f[n_] := Sum[ Floor@ Log[2, n/3^i] + 1, {i, 0, Log[3, n]}]; Table[ f[10^n], {n, 0, 46}] (* Robert G. Wilson v, Nov 07 2012 *)
PROG
(Python)
from sympy import integer_log
def A100752(n): return sum((10**n//3**i).bit_length() for i in range(integer_log(10**n, 3)[0]+1)) # Chai Wah Wu, Oct 23 2024
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Robert G. Wilson v, May 27 2005
STATUS
approved