A128952 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 3 and is not divisible by at least one of the primes 2, 5 and 7.

66, 657, 6572, 65715, 657143, 6571429, 65714286, 657142857, 6571428572, 65714285715, 657142857143, 6571428571429, 65714285714286, 657142857142857, 6571428571428572, 65714285714285715, 657142857142857143

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/3) - floor(10^n/70) + floor(10^n/210).

Example

a(6) = 10^6 - floor(10^6/3) - floor(10^6/70) + floor(10^6/210) = 1000000 - floor(333333.333...) - floor(14285.714...) + floor(4761.904...) = 1000000 - 333333 - 14285 + 4761 = 657143. - Jon E. Schoenfield, Nov 18 2018

Maple

a := n->10^n-floor(10^n/3)-floor(10^n/70)+floor(10^n/210);

Mathematica

Table[With[{c=10^n}, c-Floor[c/3]-Floor[c/70]+Floor[c/210]], {n, 2, 20}] (* Harvey P. Dale, Jun 22 2022 *)

Prog

(Magma) [10^n-Floor(10^n/3)-Floor(10^n/70)+Floor(10^n/210): n in [2..20]]; // Vincenzo Librandi, Oct 02 2011

Crossrefs

Cf. A092695.

Sequence in context: A233065 A129218 A046409 * A282050 A270258 A223410

Adjacent sequences: A128949 A128950 A128951 * A128953 A128954 A128955

Keyword

nonn

Author

Milan Janjic, Apr 28 2007

Status

approved