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8*5^n-1.
1

%I #16 Sep 08 2022 08:46:00

%S 7,39,199,999,4999,24999,124999,624999,3124999,15624999,78124999,

%T 390624999,1953124999,9765624999,48828124999,244140624999,

%U 1220703124999,6103515624999,30517578124999,152587890624999,762939453124999

%N 8*5^n-1.

%H Vincenzo Librandi, <a href="/A198767/b198767.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (6,-5).

%F a(n) = 5*a(n-1)+4.

%F a(n) = 6*a(n-1)-5*a(n-2), n>1.

%F G.f.: (7 - 3*x)/(1 - 6*x + 5*x^2). - _Vincenzo Librandi_, Jan 04 2013

%t CoefficientList[Series[(7 - 3*x)/(1 - 6*x + 5*x^2), {x, 0, 30}], x] (* _Vincenzo Librandi_, Jan 04 2013 *)

%o (Magma) [8*5^n-1: n in [0..30]];

%Y Cf. A024049, A057651, A081655.

%K nonn,easy

%O 0,1

%A _Vincenzo Librandi_, Oct 30 2011