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 A021844 #22 Sep 01 2025 17:09:50
%S A021844 1,23,363,4963,63539,787731,9609811,116281811,1401253587,16850623699,
%T A021844 202422366419,2430363281619,29172151056595,350112652220627,
%U A021844 4201633221810387,50421288464357587,605065606114711763,7260848163537557715,87130543395042760915,1045568713702569416915
%N A021844 Expansion of 1/((1-x)*(1-4*x)*(1-6*x)*(1-12*x)).
%H A021844 Vincenzo Librandi, <a href="/A021844/b021844.txt">Table of n, a(n) for n = 0..200</a>
%H A021844 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (23,-166,432,-288).
%F A021844 a(n) = 3*12^(n+1)/11 -3*6^(n+1)/5 +2^(2*n+2)/3 -1/165. - _R. J. Mathar_, Mar 15 2011
%F A021844 a(0)=1, a(1)=23, a(2)=363, a(3)=4963, a(n) = 23*a(n-1)-166*a(n-2)+432*a(n-3)-288*a(n-4). - _Harvey P. Dale_, May 11 2011
%t A021844 CoefficientList[Series[1/((1-x)(1-4x)(1-6x)(1-12x)),{x,0,40}],x] (* or *) LinearRecurrence[{23,-166,432,-288},{1,23,363,4963},40] (* _Harvey P. Dale_, May 11 2011 *)
%o A021844 (PARI) Vec(1/((1-x)*(1-4*x)*(1-6*x)*(1-12*x))+O(x^99)) \\ _Charles R Greathouse IV_, Sep 26 2012
%K A021844 nonn,easy,changed
%O A021844 0,2
%A A021844 _N. J. A. Sloane_