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 A054127 #25 Aug 01 2021 15:59:06
%S A054127 2,5,13,30,65,136,279,566,1141,2292,4595,9202,18417,36848,73711,
%T A054127 147438,294893,589804,1179627,2359274,4718569,9437160,18874343,
%U A054127 37748710,75497445,150994916,301989859,603979746,1207959521
%N A054127 a(1) = 2; a(n) = 9*2^(n-2) - n - 2, n>1.
%C A054127 Second column of A054126.
%H A054127 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (4,-5,2).
%F A054127 a(n) = A054126(n, 1).
%F A054127 G.f.: x * (2-x) * (1-x+x^2) / ( (1-x)^2 * (1-2*x) ). - _Joerg Arndt_, Dec 01 2014
%t A054127 Join[{2},Table[9*2^(n-2)-n-2,{n,2,30}]] (* _Harvey P. Dale_, Jul 16 2020 *)
%t A054127 LinearRecurrence[{4,-5,2},{2,5,13,30},30] (* _Harvey P. Dale_, Aug 01 2021 *)
%Y A054127 Cf. A054126.
%K A054127 nonn,easy
%O A054127 1,1
%A A054127 _Clark Kimberling_