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 A154968 #25 Mar 15 2024 02:23:04
%S A154968 1,1,7,40,244,1456,8752,52480,314944,1889536,11337472,68024320,
%T A154968 408146944,2448879616,14693281792,88159682560,528958111744,
%U A154968 3173748637696,19042491891712,114254951219200,685529707577344
%N A154968 a(n) = 4*a(n-1) + 12*a(n-2), n>2 with a(0)=1, a(1)=1, a(2)=7.
%H A154968 G. C. Greubel, <a href="/A154968/b154968.txt">Table of n, a(n) for n = 0..1000</a>
%H A154968 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (4,12).
%F A154968 16*a(n) = 3*6^n +(-1)^n*2^n, n>0. - _R. J. Mathar_, Sep 03 2013
%F A154968 From _G. C. Greubel_, Mar 01 2021: (Start)
%F A154968 a(n) = (6^(n+1) - (-2)^(n+1))/32 + (3/4)*[n=0].
%F A154968 E.g.f.: (exp(-2*x) + 3*exp(6*x))/16. (End)
%t A154968 LinearRecurrence[{4,12}, {1,1,7}, 40] (* _G. C. Greubel_, Mar 01 2021 *)
%o A154968 (SageMath) [1]+[(6^(n+1) - (-2)^(n+1))/32 for n in [1..40]] # _G. C. Greubel_, Mar 01 2021
%o A154968 (Magma) [n eq 0 select 1 else (6^(n+1) -(-2)^(n+1))/32: n in [0..40]]; // _G. C. Greubel_, Mar 01 2021
%Y A154968 Cf. A154929.
%K A154968 nonn,easy
%O A154968 0,3
%A A154968 _Philippe Deléham_, Jan 18 2009