A160154 - OEIS

%I #2 Mar 30 2012 17:23:10

%S 0,1,82,973,9964,99955,999946,9999937,99999928,999999919,9999999910,

%T 99999999901,999999999892,9999999999883,99999999999874,

%U 999999999999865,9999999999999856,99999999999999847,999999999999999838

%N 10^n-9n for n>=1

%C a(n) is the number of positive integers less than or equal to 10^n that have at least two distinct digits.

%D Miklos Bona, Introduction to Enumerative Combinatorics, McGraw-Hill,2007,p.5

%F O.g.f.: (x+70x^2+10x^3)/((1-x)^2*(1-10x)) E.g.f.: exp(10x)-9x*exp(x)-1

%t CoefficientList[Series[Exp[10 x] - 9 x*Exp[x] - 1, {x, 0, 20}], x]* Table[n!, {n, 0, 20}]

%Y For n>=1, a(n)=A011557-A008591

%K nonn

%O 0,3

%A _Geoffrey Critzer_, May 03 2009