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 A212323 #16 Dec 08 2023 13:40:58
%S A212323 1,2,8,25,78,238,721,2174,6540,19649,58994,177058,531297,1594090,
%T A212323 4782592,14348297,43045734,129138566,387417905,1162257286,3486777636,
%U A212323 10460342257,31381041898,94143150170,282429490113,847288534418,2541865706936,7625597288569
%N A212323 a(n) = 3^n - Fibonacci(n).
%H A212323 Bruno Berselli, <a href="/A212323/b212323.txt">Table of n, a(n) for n = 0..1000</a>
%H A212323 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (4,-2,-3).
%F A212323 G.f.: (1 - 2*x + 2*x^2)/((1 - 3*x)*(1 - x - x^2)).
%t A212323 Table[3^n - Fibonacci[n], {n, 0, 27}]
%t A212323 LinearRecurrence[{4,-2,-3},{1,2,8},30] (* _Harvey P. Dale_, Dec 08 2023 *)
%o A212323 (PARI) for(n=0, 27, print1(3^n-fibonacci(n)", "));
%o A212323 (Magma) [3^n-Fibonacci(n): n in [0..27]];
%Y A212323 Cf. A000045, A000244, A099036, A212262.
%K A212323 nonn,easy
%O A212323 0,2
%A A212323 _Bruno Berselli_, May 09 2012