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 A128951 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 5 and is not divisible by at least one of the primes 2, 3 and 7. 1
 78, 781, 7809, 78096, 780952, 7809524, 78095238, 780952381, 7809523809, 78095238096, 780952380952, 7809523809524, 78095238095238, 780952380952381, 7809523809523809, 78095238095238096, 780952380952380952 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 2..1000 Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets FORMULA a(n) = 10^n - floor(10^n/5) - floor(10^n/42) + floor(10^n/210). EXAMPLE a(6) = 10^6 - floor(10^6/5) - floor(10^6/42) + floor(10^6/210) = 1000000 - floor(200000) - floor(23809.523...) + floor(4761.904...) = 1000000 - 200000 - 23809 + 4761 = 780952. MAPLE f := n->10^n-floor(10^n/5)-floor(10^n/42)+floor(10^n/210); MATHEMATICA Table[With[{c=10^n}, c-Floor[c/5]-Floor[c/42]+Floor[c/210]], {n, 2, 20}] (* Harvey P. Dale, Nov 02 2019 *) PROG (MAGMA) [10^n-Floor(10^n/5)-Floor(10^n/42)+Floor(10^n/210): n in [2..20]]; // Vincenzo Librandi, Oct 02 2011 CROSSREFS Cf. A092695. Sequence in context: A297759 A147619 A119093 * A272383 A027786 A175383 Adjacent sequences:  A128948 A128949 A128950 * A128952 A128953 A128954 KEYWORD nonn AUTHOR Milan Janjic, Apr 28 2007 EXTENSIONS Example edited by Jon E. Schoenfield, Nov 18 2018 STATUS approved

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Last modified February 20 07:52 EST 2020. Contains 332069 sequences. (Running on oeis4.)