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 A156774 #34 Sep 08 2022 08:45:41
%S A156774 485,3482,19601,48842,91205,146690,215297,297026,391877,499850,620945,
%T A156774 755162,902501,1062962,1236545,1423250,1623077,1836026,2062097,
%U A156774 2301290,2553605,2819042,3097601,3389282,3694085,4012010,4343057,4687226
%N A156774 a(n) = 6561*n^2 - 3564*n + 485.
%C A156774 The identity (6561*n^2 - 3564*n + 485)^2 - (81*n^2 - 44*n + 6)*(729*n - 198)^2 = 1 can be written as a(n)^2 - A156676(n)*A156772(n)^2 = 1 for n>0.
%H A156774 Vincenzo Librandi, <a href="/A156774/b156774.txt">Table of n, a(n) for n = 0..10000</a>
%H A156774 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A156774 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).
%F A156774 G.f.: (485 + 2027*x + 10610*x^2)/(1-x)^3.
%F A156774 E.g.f.: (485 + 2997*x + 6561*x^2)*exp(x). - _G. C. Greubel_, Jun 21 2021
%t A156774 LinearRecurrence[{3,-3,1},{485,3482,19601},40]
%t A156774 Table[6561n^2-3564n+485,{n,0,30}] (* _Harvey P. Dale_, Dec 09 2020 *)
%o A156774 (Magma) I:=[485, 3482, 19601]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..40]];
%o A156774 (PARI) a(n)= 6561*n^2-3564*n+485 \\ _Charles R Greathouse IV_, Dec 23 2011
%o A156774 (Sage) [485 -3564*n +6561*n^2 for n in (0..40)] # _G. C. Greubel_, Jun 21 2021
%Y A156774 Cf. A156676, A156772.
%K A156774 nonn,easy
%O A156774 0,1
%A A156774 _Vincenzo Librandi_, Feb 15 2009
%E A156774 Edited by _Charles R Greathouse IV_, Jul 25 2010