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A128956 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 2,7 and is not divisible by at least one of the primes 3,5. 1
87, 867, 8667, 86668, 866667, 8666668, 86666667, 866666667, 8666666667, 86666666668, 866666666667, 8666666666668, 86666666666667, 866666666666667, 8666666666666667, 86666666666666668, 866666666666666667 (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/14) - floor(10^n/15) + floor(10^n/210).

EXAMPLE

a(6) = 10^6 - floor(10^6/14) - floor(10^6/15) + floor(10^6/210) = 1000000 - floor(71428.571...) - floor(66666.666...) + floor(4761.904...) = 1000000 - 71428 - 66666 + 4761 = 866667. - Jon E. Schoenfield, Nov 18 2018

MAPLE

f := n->10^n-floor(10^n/14)-floor(10^n/15)+floor(10^n/210);

PROG

(MAGMA) [10^n-Floor(10^n/14)-Floor(10^n/15)+Floor(10^n/210): n in [2..20]]; // Vincenzo Librandi, Oct 02 2011

CROSSREFS

Cf. A092695.

Sequence in context: A061625 A220055 A281806 * A283952 A294907 A093287

Adjacent sequences:  A128953 A128954 A128955 * A128957 A128958 A128959

KEYWORD

nonn

AUTHOR

Milan Janjic, Apr 28 2007

STATUS

approved

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Last modified January 28 23:12 EST 2022. Contains 350670 sequences. (Running on oeis4.)