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a(n) = 5*(10^n-7).
0

%I #13 Jul 04 2021 02:10:38

%S 15,465,4965,49965,499965,4999965,49999965,499999965,4999999965,

%T 49999999965,499999999965,4999999999965,49999999999965,

%U 499999999999965,4999999999999965,49999999999999965,499999999999999965

%N a(n) = 5*(10^n-7).

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).

%F G.f.: 15*x*(1+20*x) / ( (10*x-1)*(x-1) ). a(n) = 15*A033175(n-1). - _R. J. Mathar_, Jan 05 2011

%K nonn,easy

%O 1,1

%A _Vincenzo Librandi_