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 A021664 #23 Jul 08 2025 08:45:41
%S A021664 1,23,362,4894,61251,733461,8546764,97847228,1106991941,12422320339,
%T A021664 138608884206,1540404875802,17070111627271,188776494239057,
%U A021664 2084583574516688,22994756444303416,253457017948866441
%N A021664 Expansion of 1/((1-x)(1-3x)(1-8x)(1-11x)).
%H A021664 Vincenzo Librandi, <a href="/A021664/b021664.txt">Table of n, a(n) for n = 0..200</a>
%H A021664 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (23,-167,409,-264)
%F A021664 a(n) = 3^(n+3)/80 -1/140 +11^(n+3)/240 -8^(n+3)/105. - _R. J. Mathar_, Mar 15 2011
%F A021664 a(0) = 1, a(1) = 23, a(2) = 362, a(3) = 4894, a(n) = 23*a(n-1) - 167*a(n-2) + 409*a(n-3) - 264*a(n-4). - _Harvey P. Dale_, Feb 17 2015
%t A021664 CoefficientList[Series[1 / ((1 - x) (1 - 3 x) (1 - 8 x) (1 - 11 x)), {x, 0, 20}], x] (* _Vincenzo Librandi_, Jul 11 2013 *)
%t A021664 LinearRecurrence[{23, -167, 409, -264}, {1, 23, 362, 4894}, 20] (* _Harvey P. Dale_, Feb 17 2015 *)
%o A021664 (PARI) Vec(1/((1-x)*(1-3*x)*(1-8*x)*(1-11*x))+O(x^99)) \\ _Charles R Greathouse IV_, Sep 26 2012
%K A021664 nonn,easy
%O A021664 0,2
%A A021664 _N. J. A. Sloane_