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 A021694 #18 Jul 08 2025 08:48:24
%S A021694 1,24,394,5544,71995,891408,10701748,125788848,1456313749,16673208552,
%T A021694 189289198462,2135136588312,23963101915663,267883518461856,
%U A021694 2985323286760936,33185997429018336,368172943255604137
%N A021694 Expansion of 1/((1-x)(1-3x)(1-9x)(1-11x)).
%H A021694 Vincenzo Librandi, <a href="/A021694/b021694.txt">Table of n, a(n) for n = 0..200</a>
%H A021694 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (24,-182,456,-297).
%F A021694 G.f.: 1/((1-x)*(1-3*x)*(1-9*x)*(1-11*x)).
%F A021694 a(n) = -1/160 +3^(n+2)/32 -3^(2n+5)/32 +11^(n+3)/160. [_Bruno Berselli_, May 07 2013]
%F A021694 a(n)-11*a(n-1) = A006100(n+2). [_Bruno Berselli_, May 08 2013]
%t A021694 CoefficientList[Series[1/((1 - x) (1 - 3 x) (1 - 9 x) (1 - 11 x)), {x, 0, 20}], x] (* _Bruno Berselli_, May 07 2013 *)
%t A021694 LinearRecurrence[{24,-182,456,-297},{1,24,394,5544},20] (* _Harvey P. Dale_, Mar 01 2022 *)
%o A021694 (PARI) Vec(1/((1-x)*(1-3*x)*(1-9*x)*(1-11*x))+O(x^20)) \\ _Bruno Berselli_, May 07 2013
%o A021694 (Magma) m:=20; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-x)*(1-3*x)*(1-9*x)*(1-11*x)))); // _Bruno Berselli_, May 07 2013
%Y A021694 Cf. A006100, A018091 (first differences).
%K A021694 nonn,easy
%O A021694 0,2
%A A021694 _N. J. A. Sloane_