A128950 - OEIS

A128950

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.

83, 829, 8286, 82858, 828571, 8285715, 82857143, 828571429, 8285714286, 82857142858, 828571428571, 8285714285715, 82857142857143, 828571428571429, 8285714285714286, 82857142857142858, 828571428571428571

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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/7) - floor(10^n/30) + floor(10^n/210).

EXAMPLE

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.

MAPLE

f := n->10^n-floor(10^n/7)-floor(10^n/30)+floor(10^n/210);

PROG

(Magma) [10^n-Floor(10^n/7)-Floor(10^n/30)+Floor(10^n/210): n in [2..20]]; // Vincenzo Librandi, Oct 02 2011

CROSSREFS

Sequence in context: A069596 A290407 A112766 * A068851 A250083 A292284

Adjacent sequences: A128947 A128948 A128949 * A128951 A128952 A128953

KEYWORD

nonn

AUTHOR

Milan Janjic, Apr 28 2007

EXTENSIONS

Example edited by Jon E. Schoenfield, Nov 17 2018

STATUS

approved