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3*6^n-1.
3

%I #15 Sep 08 2022 08:46:00

%S 2,17,107,647,3887,23327,139967,839807,5038847,30233087,181398527,

%T 1088391167,6530347007,39182082047,235092492287,1410554953727,

%U 8463329722367,50779978334207,304679870005247,1828079220031487

%N 3*6^n-1.

%H Vincenzo Librandi, <a href="/A198796/b198796.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (7,-6).

%F a(n) = 6*a(n-1)+5. a(n) = 7*a(n-1)-6*a(n-2), n>1.

%F G.f.: ( 2+3*x ) / ( (6*x-1)*(x-1) ). - _R. J. Mathar_, Oct 30 2011

%t Table[3*6^n-1,{n,0,30}] (* or *) LinearRecurrence[{7,-6},{2,17},30] (* _Harvey P. Dale_, May 22 2016 *)

%o (Magma) [3*6^n-1: n in [0..30]]

%K nonn,easy

%O 0,1

%A _Vincenzo Librandi_, Oct 30 2011