A125947 a(n) is the number of nonnegative integers k less than 10^n such that the decimal representation of k lacks the digit 1, at least one of digits 2,3,4,5 and at least one of digits 6,7,8,9.

9, 81, 729, 6513, 57369, 495921, 4194969, 34689393, 280607769, 2224214961, 17313344409, 132651929073, 1002605145369, 7490229758001, 55407572177049, 406450276733553, 2960529995462169, 21435301615525041, 154414691892116889, 1107604165960750833

Offset: 1

Author

Aleksandar M. Janjic and Milan Janjic, Feb 04 2007

Keywords

• nonn
• base
• easy

Examples

			a(8) = 34689393.
		

Links

• Colin Barker, Table of n, a(n) for n = 1..1000
• Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
• Index entries for linear recurrences with constant coefficients, signature (28,-322,1960,-6769,13132,-13068,5040).

Crossrefs

Cf. A125630.

Programs

Maple

f:=n->16*7^n-48*6^n+68*5^n-56*4^n+28*3^n-8*2^n+1;

Mathematica

Table[ 16*7^n-48*6^n+68*5^n-56*4^n+28*3^n-8*2^n+1, {n, 20}] (* James C. McMahon, Dec 23 2024 *)

PARI

Vec(-3*x*(1680*x^6 -3988*x^5 +3968*x^4 -1819*x^3 +453*x^2-57*x+3) / ((x -1)*(2*x -1)*(3*x -1)*(4*x -1)*(5*x -1)*(6*x -1)*(7*x -1)) + O(x^100)) \\ Colin Barker, Feb 22 2015

Formula

a(n) = 16*7^n-48*6^n+68*5^n-56*4^n+28*3^n-8*2^n+1.

G.f.: -3*x*(1680*x^6 -3988*x^5 +3968*x^4 -1819*x^3 +453*x^2-57*x+3) / ((x -1)*(2*x -1)*(3*x -1)*(4*x -1)*(5*x -1)*(6*x -1)*(7*x -1)). - Colin Barker, Feb 22 2015