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A126627 a(n) is the number of nonnegative integers k less than 10^n such that the decimal representation of k lacks digits 1,2,3 and at least one of digits 4,5,6,7,8,9.

%I A126627 #12 Aug 02 2017 11:30:09
%S A126627 7,49,343,2401,16807,116929,803383,5432161,36120007,236404609,
%T A126627 1525601623,9726181921,61371928807,383929313089,2384606035063,
%U A126627 14723095123681,90457525939207,553507860826369,3375536272503703,20528377102849441,124556950506727207
%N A126627 a(n) is the number of nonnegative integers k less than 10^n such that the decimal representation of k lacks digits 1,2,3 and at least one of digits 4,5,6,7,8,9.
%H A126627 Colin Barker, <a href="/A126627/b126627.txt">Table of n, a(n) for n = 1..1000</a>
%H A126627 Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas for Some Functions on Finite Sets</a>
%H A126627 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (21,-175,735,-1624,1764,-720).
%F A126627 a(n) = 6*6^n-15*5^n+20*4^n-15*3^n+6*2^n-1.
%F A126627 G.f.: -x*(720*x^5 -1764*x^4 +1372*x^3 -539*x^2 +98*x -7) / ((x -1)*(2*x -1)*(3*x -1)*(4*x -1)*(5*x -1)*(6*x -1)). - _Colin Barker_, Feb 23 2015
%p A126627 f:=n->6*6^n-15*5^n+20*4^n-15*3^n+6*2^n-1;
%t A126627 LinearRecurrence[{21,-175,735,-1624,1764,-720},{7,49,343,2401,16807,116929},30] (* _Harvey P. Dale_, Aug 02 2017 *)
%o A126627 (PARI) vector(100, n, 6*6^n-15*5^n+20*4^n-15*3^n+6*2^n-1) \\ _Colin Barker_, Feb 23 2015
%Y A126627 Cf. A125630, A125948, A125947, A125946, A125945, A125910, A125909, A125908, A125880, A125897, A125904, A125858.
%K A126627 nonn,base,easy
%O A126627 1,1
%A A126627 Aleksandar M. Janjic and _Milan Janjic_, Feb 08 2007