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A128959 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 2,3 and is not divisible by at least one of the primes 5,7. 1
82, 810, 8096, 80953, 809524, 8095239, 80952382, 809523810, 8095238096, 80952380953, 809523809524, 8095238095239, 80952380952382, 809523809523810, 8095238095238096, 80952380952380953, 809523809523809524, 8095238095238095239, 80952380952380952382 (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

Index entries for linear recurrences with constant coefficients, signature (11,-11,11,-11,11,-10).

FORMULA

a(n) = 10^n-floor(10^n/6)-floor(10^n/35)+floor(10^n/210).

From Colin Barker, Nov 17 2015: (Start)

a(n) = 11*a(n-1)-11*a(n-2)+11*a(n-3)-11*a(n-4)+11*a(n-5)-10*a(n-6) for n>7.

G.f.: -x^2*(90*x^5-89*x^4+95*x^3-88*x^2+92*x-82) / ((x-1)*(10*x-1)*(x^2-x+1)*(x^2+x+1)).

(End)

MAPLE

f := n->10^n-floor(10^n/2)-floor(10^n/35)+floor(10^n/210);

PROG

(MAGMA) [10^n-Floor(10^n/6)-Floor(10^n/35)+Floor(10^n/210): n in [2..20]]; // Vincenzo Librandi, Oct 02 2011

(PARI) Vec(-x^2*(90*x^5-89*x^4+95*x^3-88*x^2+92*x-82)/((x-1)*(10*x-1)*(x^2-x+1)*(x^2+x+1)) + O(x^30)) \\ Colin Barker, Nov 17 2015

CROSSREFS

Cf. A092695.

Sequence in context: A182277 A186688 A002309 * A305682 A317062 A230394

Adjacent sequences:  A128956 A128957 A128958 * A128960 A128961 A128962

KEYWORD

nonn,easy

AUTHOR

Milan Janjic, Apr 28 2007

STATUS

approved

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Last modified December 17 14:12 EST 2018. Contains 318201 sequences. (Running on oeis4.)