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 A121203 #25 Sep 03 2024 15:03:09
%S A121203 0,4,28,224,1784,13692,102036,745432,5374192,38400500,272709644,
%T A121203 1928498640,13597146600,95668307308,672119557252,4717043931848,
%U A121203 33080342679008,231867574534116,1624598900644860,11379821699045056
%N A121203 a(n) = 2n+7^n-5^n.
%H A121203 Vincenzo Librandi, <a href="/A121203/b121203.txt">Table of n, a(n) for n = 0..1000</a>
%H A121203 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (14,-60,82,-35).
%F A121203 G.f.: 4*x*(1-7*x+18*x^2)/((1-x)^2*(1-5*x)*(1-7*x)). - _Vincenzo Librandi_, Feb 25 2013
%F A121203 a(n) = 14*a(n-1)-60*a(n-2)+82*a(n-3)-35*a(n-4). - _Vincenzo Librandi_, Feb 26 2013
%t A121203 CoefficientList[Series[4 x (1 - 7 x + 18 x^2)/((1-x)^2 (1-5 x)(1-7 x)), {x, 0, 30}], x] (* _Vincenzo Librandi_, Feb 25 2013 *)
%o A121203 (Magma) [2*n+7^n-5^n: n in [0..30]]; // _Vincenzo Librandi_, Feb 26 2013
%o A121203 (Magma) I:=[0,4,28,224]; [n le 4 select I[n] else 14*Self(n-1)-60*Self(n-2)+82*Self(n-3)-35*Self(n-4): n in [1..20]]; // _Vincenzo Librandi_, Feb 26 2013
%Y A121203 Cf. A074616.
%K A121203 nonn,easy
%O A121203 0,2
%A A121203 _Mohammad K. Azarian_, Aug 19 2006
%E A121203 Edited by _Ray Chandler_, Sep 06 2006