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.

50, 495, 4952, 49524, 495238, 4952381, 49523810, 495238095, 4952380952, 49523809524, 495238095238, 4952380952381, 49523809523810, 495238095238095, 4952380952380952, 49523809523809524, 495238095238095238

Offset: 2

Author

Milan Janjic, Apr 28 2007

Keywords

• nonn

Examples

			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
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 2..1000
• Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets

Crossrefs

Cf. A092695.

Programs

Magma

[10^n-Floor(10^n/2)-Floor(10^n/105)+Floor(10^n/210): n in [2..20]]; // Vincenzo Librandi, Oct 02 2011

Maple

f := n->10^n-floor(10^n/2)-floor(10^n/105)+floor(10^n/210);

Formula

a(n) = 10^n - floor(10^n/2) - floor(10^n/105) + floor(10^n/210).