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 A016212 #23 Feb 15 2021 16:26:40 %S A016212 1,11,90,670,4811,34041,239380,1678940,11762421,82366471,576653870, %T A016212 4036842810,28258696831,197813269301,1384700059560,9692921940280, %U A016212 67850518152041,474953820774531,3324677326552450,23272743029259350,162909206434992051,1140364460735474161 %N A016212 Expansion of 1/((1-x)*(1-3*x)*(1-7*x)). %H A016212 Matthew House, <a href="/A016212/b016212.txt">Table of n, a(n) for n = 0..1177</a> %H A016212 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (11,-31,21). %F A016212 a(0)=1, a(1)=11, a(n) = 10*a(n-1) - 21*a(n-2) + 1. - _Vincenzo Librandi_, Feb 10 2011 %F A016212 a(n) = (7^(n+2) - 3^(n+3) + 2)/24. - _Yahia Kahloune_, May 06 2013 %F A016212 a(n) = 11*a(n-1) - 31*a(n-2) + 21*a(n-3). - _Matthew House_, Jan 13 2017 %p A016212 a:=n->sum((7^(n-j)-3^(n-j))/4,j=0..n): seq(a(n), n=1..19); # _Zerinvary Lajos_, Jan 15 2007 %o A016212 (PARI) Vec(1/((1-x)*(1-3*x)*(1-7*x))+O(x^99)) \\ _Charles R Greathouse IV_, Sep 26 2012 %K A016212 nonn,easy %O A016212 0,2 %A A016212 _N. J. A. Sloane_