This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A185940 #31 Sep 08 2022 08:45:55
%S A185940 24,74,228,698,2124,6434,19428,58538,176124,529394,1590228,4774778,
%T A185940 14332524,43013954,129074628,387289418,1161999324,3486260114,
%U A185940 10459304628,31378962458,94138984524,282421147874,847271832228,2541832273898,7625530376124,22876658237234
%N A185940 a(n) = 1 - 2^(n+1) + 3^(n+2).
%H A185940 G. C. Greubel, <a href="/A185940/b185940.txt">Table of n, a(n) for n = 1..1000</a>
%H A185940 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (6,-11,6).
%F A185940 a(n) = 1 - A000079(n+1) + A000244(n+2)
%F A185940 From _Alexander R. Povolotsky_, Jan 07 2011: (Start)
%F A185940 G.f.: 2*x*(12 - 35*x + 24*x^2) / (1 - 6*x + 11*x^2 - 6*x^3)
%F A185940 a(n+2) = -6*a(n) + 5*a(n+1)+2. (End)
%F A185940 a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3). - _G. C. Greubel_, Feb 25 2017
%F A185940 E.g.f.: exp(x) - 2*exp(2*x) + 9*exp(3*x) - 8. - _G. C. Greubel_, Jul 23 2017
%p A185940 A185940:=n->1-2^(n+1)+3^(n+2): seq(A185940(n), n=1..40); # _Wesley Ivan Hurt_, Jul 23 2017
%t A185940 CoefficientList[Series[-2*x*(12 - 35*x + 24*x^2)/(-1 + 6*x - 11*x^2 + 6*x^3), {x,0,50}], x] (* or *) LinearRecurrence[{6, -11, 6}, {24, 74, 228}, 50] (* _G. C. Greubel_, Feb 25 2017 *)
%o A185940 (Magma) [1 - 2^(n+1) + 3^(n+2): n in [1..40]]; // _Vincenzo Librandi_, Apr 05 2011
%o A185940 (PARI) x='x+O('x^50); Vec(-2*x*(12 - 35*x + 24*x^2) / (-1 + 6*x - 11*x^2 + 6*x^3)) \\ _G. C. Greubel_, Feb 25 2017
%Y A185940 Cf. A000079, A000244, A066280.
%K A185940 nonn,easy
%O A185940 1,1
%A A185940 _Amir H. Farrahi_, Feb 06 2011
%E A185940 Corrected and edited by _Bruno Berselli_, Apr 04 2011