%I #24 Sep 08 2022 08:46:00

%S 4,28,244,2188,19684,177148,1594324,14348908,129140164,1162261468,

%T 10460353204,94143178828,847288609444,7625597484988,68630377364884,

%U 617673396283948,5559060566555524,50031545098999708,450283905890997364

%N a(n) = 3*9^n+1.

%C An Engel expansion of 3 to the base 9 as defined in A181565, with the associated series expansion 3 = 9/4 + 9^2/(4*28) + 9^3/(4*28*244) + 9^4/(4*28*244*2188) + .... Cf. A087289 and A207262. - _Peter Bala_, Oct 29 2013

%H Vincenzo Librandi, <a href="/A199561/b199561.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 (10,-9).

%F a(n) = 4*A066443(n).

%F a(n) = 9*a(n-1)-8.

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

%F G.f.: 4*(1-3*x)/((1-x)*(1-9*x)).

%t 3*9^Range[0,20]+1 (* or *) LinearRecurrence[{10,-9},{4,28},20] (* _Harvey P. Dale_, Jul 30 2019 *)

%o (Magma) [3*9^n+1: n in [0..30]];

%Y Cf. A087289, A207262.

%K nonn,easy

%O 0,1

%A _Vincenzo Librandi_, Nov 08 2011