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A128950
a(n) is equal to the number of positive integers m less than or equal to 10^n such that m is not divisible by the prime 7 and is not divisible by at least one of the primes 2, 3 and 5.
1
83, 829, 8286, 82858, 828571, 8285715, 82857143, 828571429, 8285714286, 82857142858, 828571428571, 8285714285715, 82857142857143, 828571428571429, 8285714285714286, 82857142857142858, 828571428571428571
OFFSET
2,1
FORMULA
a(n) = 10^n - floor(10^n/7) - floor(10^n/30) + floor(10^n/210).
EXAMPLE
a(6) = 10^6 - floor(10^6/7) - floor(10^6/30) + floor(10^6/210) = 1000000 - floor(142857.142...) - floor(33333.333...) + floor(4761.904...) = 1000000 - 142857 - 33333 + 4761 = 828571.
MAPLE
f := n->10^n-floor(10^n/7)-floor(10^n/30)+floor(10^n/210);
PROG
(Magma) [10^n-Floor(10^n/7)-Floor(10^n/30)+Floor(10^n/210): n in [2..20]]; // Vincenzo Librandi, Oct 02 2011
CROSSREFS
Sequence in context: A069596 A290407 A112766 * A068851 A250083 A292284
KEYWORD
nonn
AUTHOR
Milan Janjic, Apr 28 2007
EXTENSIONS
Example edited by Jon E. Schoenfield, Nov 17 2018
STATUS
approved