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 A080250 #22 Sep 08 2022 08:45:09
%S A080250 1,35,871,19215,402591,8236095,166570111,3349906175,67183250431,
%T A080250 1345516627455,26928850135551,538762184167935,10777095520297471,
%U A080250 215560428864815615,4311393762242888191,86229727095755178495
%N A080250 Expansion of 1/((1-x)(1-4x)(1-10x)(1-20x)).
%C A080250 Column k=3 in number triangle A080249.
%H A080250 Vincenzo Librandi, <a href="/A080250/b080250.txt">Table of n, a(n) for n = 0..300</a>
%H A080250 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (35,-354,1120,-800).
%F A080250 G.f.: 1/((1-x)*(1-4*x)*(1-10*x)*(1-20*x)).
%F A080250 a(n) = (1350*20^n-950*10^n+114*4^n-1)/513.
%F A080250 a(0)=1, a(1)=35, a(2)=871, a(3)=19215, a(n) = 35*a(n-1) -354*a(n-2) +1120*a(n-3) -800*a(n-4). - _Harvey P. Dale_, Apr 25 2011
%t A080250 CoefficientList[Series[1/((1-x)(1-4x)(1-10x)(1-20x)),{x,0,20}],x] (* or *) Table[(1350*20^n-950*10^n+114*4^n-1)/513,{n,0,20}] (* or *) LinearRecurrence[{35,-354,1120,-800},{1,35,871,19215},21] (* _Harvey P. Dale_, Apr 25 2011 *)
%o A080250 (Magma) [(1350*20^n-950*10^n+114*4^n-1)/513: n in [0..20]]; // _Vincenzo Librandi_, Aug 05 2013
%Y A080250 Cf. A080249, A016225, A000292.
%K A080250 easy,nonn
%O A080250 0,2
%A A080250 _Paul Barry_, Feb 17 2003
%E A080250 Corrected by _T. D. Noe_, Nov 08 2006