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 A138233 #12 Mar 11 2023 08:14:42
%S A138233 5,35,275,2315,20195,179195,1602515,14381675,129271235,1162785755,
%T A138233 10462450355,94151567435,847322163875,7625731702715,68630914235795,
%U A138233 617675543767595,5559069156490115,50031579458738075,450284043329950835
%N A138233 a(n) = 2^(2*n+1) + 3^(2*n+1).
%C A138233 Subsequence of A008587.
%H A138233 G. C. Greubel, <a href="/A138233/b138233.txt">Table of n, a(n) for n = 0..1000</a>
%H A138233 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (13,-36).
%F A138233 a(n) = 5*A096951(n).
%F A138233 a(n+1) = 4*a(n) + 5*3^(2*n+1), a(0) = 5.
%F A138233 O.g.f.: 5*x*(7-36*x)/((1-4*x)*(1-9*x)). - _R. J. Mathar_, Apr 24 2008
%F A138233 E.g.f.: 2*exp(4*x) + 3*exp(9*x). - _G. C. Greubel_, Mar 11 2023
%t A138233 LinearRecurrence[{13, -36},{5, 35},19] (* _Ray Chandler_, Jul 14 2017 *)
%t A138233 2^#+3^#&/@(2*Range[0,20]+1) (* _Harvey P. Dale_, Sep 25 2019 *)
%o A138233 (Magma) [2^(2*n+1) + 3^(2*n+1): n in [0..30]]; // _G. C. Greubel_, Mar 11 2023
%o A138233 (SageMath) [2^(2*n+1) + 3^(2*n+1) for n in range(31)] # _G. C. Greubel_, Mar 11 2023
%Y A138233 Cf. A008587, A096951, A138199.
%K A138233 nonn
%O A138233 0,1
%A A138233 _Reinhard Zumkeller_, Mar 07 2008