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A128959
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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 at least one of the primes 2,3 and is not divisible by at least one of the primes 5,7.
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1
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82, 810, 8096, 80953, 809524, 8095239, 80952382, 809523810, 8095238096, 80952380953, 809523809524, 8095238095239, 80952380952382, 809523809523810, 8095238095238096, 80952380952380953, 809523809523809524, 8095238095238095239, 80952380952380952382
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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/6)-floor(10^n/35)+floor(10^n/210).
a(n) = 11*a(n-1)-11*a(n-2)+11*a(n-3)-11*a(n-4)+11*a(n-5)-10*a(n-6) for n>7.
G.f.: -x^2*(90*x^5-89*x^4+95*x^3-88*x^2+92*x-82) / ((x-1)*(10*x-1)*(x^2-x+1)*(x^2+x+1)).
(End)
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MAPLE
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f := n->10^n-floor(10^n/2)-floor(10^n/35)+floor(10^n/210);
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PROG
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(Magma) [10^n-Floor(10^n/6)-Floor(10^n/35)+Floor(10^n/210): n in [2..20]]; // Vincenzo Librandi, Oct 02 2011
(PARI) Vec(-x^2*(90*x^5-89*x^4+95*x^3-88*x^2+92*x-82)/((x-1)*(10*x-1)*(x^2-x+1)*(x^2+x+1)) + O(x^30)) \\ Colin Barker, Nov 17 2015
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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