A198974 - OEIS

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

%S 1,21,241,2661,29281,322101,3543121,38974341,428717761,4715895381,

%T 51874849201,570623341221,6276856753441,69045424287861,

%U 759499667166481,8354496338831301,91899459727144321,1010894056998587541,11119834626984462961

%N 2*11^n-1.

%H Vincenzo Librandi, <a href="/A198974/b198974.txt">Table of n, a(n) for n = 0..900</a>

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (12,-11).

%F a(n) = 11*a(n-1)+10.

%F a(n) = 12*a(n-1)-11*a(n-2), n>1.

%F G.f.: (1 + 9*x)/(1 - 12*x + 11*x^2). - _Vincenzo Librandi_, Jan 04 2013

%t CoefficientList[Series[(1 + 9*x)/(1 - 12*x + 11*x^2), {x, 0, 30}], x] (* _Vincenzo Librandi_, Jan 04 2013 *)

%t 2*11^Range[0,20]-1 (* or *) LinearRecurrence[{12,-11},{1,21},20] (* _Harvey P. Dale_, Dec 25 2019 *)

%o (Magma) [2*11^n-1 : n in [0..20]]

%K nonn,easy

%O 0,2

%A _Vincenzo Librandi_, Nov 02 2011