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%I #11 Jun 13 2015 00:52:18
%S 5,25,125,601,2765,12265,52925,223801,932525,3844105,15722525,
%T 63936601,258902285,1045109545,4209004925,16921851001,67945160045,
%U 272554432585,1092540156125,4377129999001,17529432313805,70180474597225,280910151192125
%N a(n) is the number of integers k less than 10^n such that the decimal representation of k lacks the digits 1,2,3,4 and 5 and at least one of digits 6,7,8,9.
%H Colin Barker, <a href="/A126642/b126642.txt">Table of n, a(n) for n = 1..1000</a>
%H Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas for Some Functions on Finite Sets</a>
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (10,-35,50,-24).
%F a(n) = 4*4^n-6*3^n+4*2^n-1.
%F a(n) = 10*a(n-1)-35*a(n-2)+50*a(n-3)-24*a(n-4). - _Colin Barker_, Feb 22 2015
%F G.f.: -x*(24*x^3-50*x^2+25*x-5) / ((x-1)*(2*x-1)*(3*x-1)*(4*x-1)). - _Colin Barker_, Feb 22 2015
%p f:=n->4*4^n-6*3^n+4*2^n-1;
%o (PARI) Vec(-x*(24*x^3-50*x^2+25*x-5) / ((x-1)*(2*x-1)*(3*x-1)*(4*x-1)) + O(x^100)) \\ _Colin Barker_, Feb 22 2015
%Y Cf. A125630, A125948, A125947, A125946, A125945, A125940, A125909, A125908, A125880, A125897, A125904, A125858.
%K nonn,base,easy
%O 1,1
%A Aleksandar M. Janjic and _Milan Janjic_, Feb 08 2007
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