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 A328606 #23 Dec 13 2019 05:51:27 %S A328606 1,11,33,187,737,3531,15169,69179,305217,1371403,6100193,27285819, %T A328606 121673761,543491531,2425394433,10829195707,48337730177,215796613131, %U A328606 963308258209,4300379260859,19197149362017,85698470593483,382565584169153,1707814344866619,7623850115593921,34033658024720651 %N A328606 Expansion of (1 + 9*x) / (1 - 2*x - 11*x^2). %H A328606 Colin Barker, <a href="/A328606/b328606.txt">Table of n, a(n) for n = 0..1000</a> %H A328606 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,11). %F A328606 a(n) = 2*a(n-1) + 11*a(n-2) for n>1. - _Colin Barker_, Oct 21 2019 %F A328606 a(n)/a(n-1) ~ 1 + 2*sqrt(3). %o A328606 (PARI) Vec((1 + 9*x) / (1 - 2*x - 11*x^2) + O(x^30)) \\ _Colin Barker_, Dec 13 2019 %Y A328606 Cf. A328604, A328605. %K A328606 nonn,easy %O A328606 0,2 %A A328606 _Kyle MacLean Smith_, Oct 20 2019