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(7*9^n+1)/4.
1

%I #12 Sep 08 2022 08:46:00

%S 2,16,142,1276,11482,103336,930022,8370196,75331762,677985856,

%T 6101872702,54916854316,494251688842,4448265199576,40034386796182,

%U 360309481165636,3242785330490722,29185067974416496,262665611769748462

%N (7*9^n+1)/4.

%H Vincenzo Librandi, <a href="/A199565/b199565.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 (10,-9).

%F a(n) = 2*A187709(n).

%F a(n) = 9*a(n-1)-2.

%F a(n) = 10*a(n-1)-9*a(n-2).

%F G.f.: 2*(1-2*x)/((1-x)*(1-9*x)).

%t LinearRecurrence[{10,-9},{2,16},30] (* _Harvey P. Dale_, Mar 14 2015 *)

%o (Magma) [(7*9^n+1)/4: n in [0..30]];

%K nonn,easy

%O 0,1

%A _Vincenzo Librandi_, Nov 08 2011