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A128950
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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.
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1
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83, 829, 8286, 82858, 828571, 8285715, 82857143, 828571429, 8285714286, 82857142858, 828571428571, 8285714285715, 82857142857143, 828571428571429, 8285714285714286, 82857142857142858, 828571428571428571
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OFFSET
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2,1
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LINKS
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FORMULA
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a(n) = 10^n - floor(10^n/7) - floor(10^n/30) + floor(10^n/210).
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EXAMPLE
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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.
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MAPLE
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f := n->10^n-floor(10^n/7)-floor(10^n/30)+floor(10^n/210);
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PROG
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(Magma) [10^n-Floor(10^n/7)-Floor(10^n/30)+Floor(10^n/210): n in [2..20]]; // Vincenzo Librandi, Oct 02 2011
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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