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 A015611 #30 Dec 30 2023 23:42:01
%S A015611 0,1,12,151,1896,23809,298980,3754423,47145936,592032193,7434407868,
%T A015611 93357119767,1172326292280,14721415345729,184863268194708,
%U A015611 2321409125756599,29150952386442144,366061292517601921,4596792176916318060,57723935170619030167
%N A015611 a(n) = 12*a(n-1) + 7*a(n-2).
%H A015611 Vincenzo Librandi, <a href="/A015611/b015611.txt">Table of n, a(n) for n = 0..900</a>
%H A015611 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (12,7).
%F A015611 G.f.: x/(1 - 12*x - 7*x^2). - _Vincenzo Librandi_, Nov 22 2012
%t A015611 Join[{a=0,b=1},Table[c=12*b+7*a;a=b;b=c,{n,60}]] (* _Vladimir Joseph Stephan Orlovsky_, Jan 31 2011 *)
%t A015611 CoefficientList[Series[x/(1 - 12x - 7x^2), {x, 0, 30}], x] (* or *) LinearRecurrence[{12, 7}, {0, 1}, 30] (* _Vincenzo Librandi_, Nov 22 2012 *)
%o A015611 (Sage) [lucas_number1(n,12,-7) for n in range(0, 18)] # _Zerinvary Lajos_, Apr 29 2009
%o A015611 (Magma) [n le 2 select n-1 else 12*Self(n-1) + 7*Self(n-2): n in [1..30]]; // _Vincenzo Librandi_, Nov 22 2012
%o A015611 (PARI) x='x+O('x^30); concat([0], Vec(x/(1-12*x-7*x^2))) \\ _G. C. Greubel_, Dec 30 2017
%K A015611 nonn,easy
%O A015611 0,3
%A A015611 _Olivier Gérard_