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 A165510 #19 Sep 08 2022 08:45:47
%S A165510 1,9,63,585,3951,38169,246303,2501865,15231951,164902329,931798143,
%T A165510 10941169545,56148296751,731615910489,3311061455583,49365284099625,
%U A165510 189031140702351,3365269314470649,10244972816098623,232054417825788105
%N A165510 a(0)=1, a(1)=9, a(n) = 72*a(n-2) - a(n-1).
%C A165510 a(n)/a(n-1) tends to -9.
%C A165510 First term < 0: a(27) = -60053864762402471338497.
%H A165510 Harvey P. Dale, <a href="/A165510/b165510.txt">Table of n, a(n) for n = 0..1000</a>
%H A165510 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (-1, 72).
%F A165510 G.f.: (1+10*x)/(1+x-72*x^2).
%F A165510 a(n) = Sum_{k=0..n} A112555(n,k)*8^k.
%F A165510 a(n) = (18*8^n-(-9)^n)/17. - _Klaus Brockhaus_, Sep 26 2009
%F A165510 E.g.f.: (18*exp(8*x) - exp(-9*x))/17. - _G. C. Greubel_, Oct 21 2018
%t A165510 LinearRecurrence[{-1,72},{1,9},30] (* _Harvey P. Dale_, Oct 15 2012 *)
%o A165510 (PARI) vector(30, n, n--; (18*8^n-(-9)^n)/17) \\ _G. C. Greubel_, Oct 21 2018
%o A165510 (Magma) [(18*8^n-(-9)^n)/17: n in [0..30]]; // _G. C. Greubel_, Oct 21 2018
%K A165510 sign
%O A165510 0,2
%A A165510 _Philippe Deléham_, Sep 21 2009