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 A189741 #34 Feb 18 2024 03:35:24
%S A189741 4,2,16,68,304,1352,6016,26768,119104,529952,2358016,10491968,
%T A189741 46683904,207719552,924246016,4112423168,18298184704,81417585152,
%U A189741 362266710016,1611902010368,7172141461504,31912369866752,141993762390016,631799789293568,2811186681954304
%N A189741 a(1)=4, a(2)=2, a(n) = 4*a(n-1) + 2*a(n-2).
%H A189741 Vincenzo Librandi, <a href="/A189741/b189741.txt">Table of n, a(n) for n = 1..100</a>
%H A189741 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (4,2).
%F A189741 G.f.: 2*x*(2-7*x)/(1-4*x-2*x^2). - _Bruno Berselli_, May 24 2011
%t A189741 LinearRecurrence[{4,2},{4,2},40]
%o A189741 (Maxima) a[1]:4$ a[2]:2$ a[n]:=4*a[n-1]+2*a[n-2]$ makelist(a[n], n, 1, 25); /* _Bruno Berselli_, May 24 2011 */
%Y A189741 Cf. A000045, A000079, A105476, A159612, A080040, A135522, A103435, A189732, A189734, A189735, A189736, A189737, A189738, A189739, A189742, A189743, A189744, A189745, A189746, A189747, A189748, A189749.
%K A189741 nonn,easy
%O A189741 1,1
%A A189741 _Harvey P. Dale_, Apr 26 2011