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 A143079 #20 Jun 29 2023 23:36:13
%S A143079 1,9,90,972,11016,128304,1516320,18055872,215830656,2584929024,
%T A143079 30988915200,371685583872,4459138615296,53503133036544,
%U A143079 641998414356480,7703745879785472,92443540002471936,1109314016699940864
%N A143079 a(n) = ((9+sqrt(9))^n + (9-sqrt(9))^n)/2.
%C A143079 Equals A007318^9 * [1, 0, 9, 0, 81, 0, 729, ...]. - _Gary W. Adamson_, Oct 23 2008
%H A143079 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (18, -72).
%F A143079 From _Philippe Deléham_, Oct 18 2008: (Start)
%F A143079 a(n) = 18*a(n-1) - 72*a(n-2).
%F A143079 a(n) = 6^n*(2^n+1)/2.
%F A143079 G.f.: (1-9x)/(1-18x+72x^2). (End)
%F A143079 From _R. J. Mathar_, Oct 21 2008: (Start)
%F A143079 a(n) = (12^n + 6^n)/2.
%F A143079 G.f.: (1-9x)/((1-12x)(1-6x)). (End)
%F A143079 a(n) = 3^n*A007582(n) = (6^n+12^n)/2 = A000051(n)*A000079(n)*A000244(n)/2. - _M. F. Hasler_, Oct 22 2008
%F A143079 A007318^9 * [1, 0, 9, 0, 81, 0, 729, ...] produces this sequence. - _Gary W. Adamson_, Oct 23 2008
%F A143079 a(n) = Sum_{k=0..n} A098158(n,k)*9^k. - _Philippe Deléham_, Oct 23 2008
%o A143079 (PARI) A143079(n)=3^n*(1+1<<n)<<(n-1) \\ _M. F. Hasler_, Oct 22 2008
%K A143079 nonn
%O A143079 0,2
%A A143079 Al Hakanson (hawkuu(AT)gmail.com), Oct 15 2008
%E A143079 Extended by _R. J. Mathar_ and _M. F. Hasler_, Oct 21 2008