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A128954 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 2 and is not divisible by at least one of the primes 3, 5 and 7.

%I A128954 #14 Sep 08 2022 08:45:30
%S A128954 50,495,4952,49524,495238,4952381,49523810,495238095,4952380952,
%T A128954 49523809524,495238095238,4952380952381,49523809523810,
%U A128954 495238095238095,4952380952380952,49523809523809524,495238095238095238
%N A128954 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 2 and is not divisible by at least one of the primes 3, 5 and 7.
%H A128954 Vincenzo Librandi, <a href="/A128954/b128954.txt">Table of n, a(n) for n = 2..1000</a>
%H A128954 Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas for Some Functions on Finite Sets</a>
%F A128954 a(n) = 10^n - floor(10^n/2) - floor(10^n/105) + floor(10^n/210).
%e A128954 a(6) = 10^6 - floor(10^6/2) - floor(10^6/105) + floor(10^6/210) = 1000000 - floor(500000) - floor(9523.809...) + floor(4761.904...) = 1000000 - 500000 - 9523 + 4761 = 495238. - _Jon E. Schoenfield_, Nov 18 2018
%p A128954 f := n->10^n-floor(10^n/2)-floor(10^n/105)+floor(10^n/210);
%o A128954 (Magma) [10^n-Floor(10^n/2)-Floor(10^n/105)+Floor(10^n/210): n in [2..20]]; // _Vincenzo Librandi_, Oct 02 2011
%Y A128954 Cf. A092695.
%K A128954 nonn
%O A128954 2,1
%A A128954 _Milan Janjic_, Apr 28 2007