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 A165505 #16 Sep 08 2022 08:45:47
%S A165505 1,7,35,259,1211,9667,41195,364819,1365371,13957027,43388555,
%T A165505 542806579,1279512731,21518363587,32221171115,871550099539,
%U A165505 481739087291,36123365093347,-15890323427125,1533071657347699,-2200465241286949
%N A165505 a(0)=1, a(1)=7, a(n) = 42*a(n-2) - a(n-1).
%C A165505 a(n)/a(n-1) tends to -7.
%H A165505 G. C. Greubel, <a href="/A165505/b165505.txt">Table of n, a(n) for n = 0..1000</a>
%H A165505 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (-1,42).
%F A165505 G.f.: (1+8*x)/(1+x-42*x^2).
%F A165505 a(n) = Sum_{k=0..n} A112555(n,k)*6^k.
%F A165505 a(n) = (14*6^n-(-7)^n)/13. - _Klaus Brockhaus_, Sep 26 2009
%F A165505 E.g.f.: (14*exp(6*x) - exp(-7*x))/13. - _G. C. Greubel_, Oct 20 2018
%p A165505 A165505:=n->(14*6^n-(-7)^n)/13: seq(A165505(n), n=0..30); # _Wesley Ivan Hurt_, Apr 14 2017
%t A165505 LinearRecurrence[{-1, 42}, {1, 7}, 40] (* _G. C. Greubel_, Oct 20 2018 *)
%o A165505 (PARI) vector(40, n, n--; (14*6^n-(-7)^n)/13) \\ _G. C. Greubel_, Oct 20 2018
%o A165505 (Magma) [(14*6^n-(-7)^n)/13: n in [0..40]]; // _G. C. Greubel_, Oct 20 2018
%K A165505 easy,sign
%O A165505 0,2
%A A165505 _Philippe Deléham_, Sep 21 2009