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 A173247 #25 Sep 08 2022 08:45:50
%S A173247 -1,3,-7,14,-24,37,-53,72,-94,119,-147,178,-212,249,-289,332,-378,427,
%T A173247 -479,534,-592,653,-717,784,-854,927,-1003,1082,-1164,1249,-1337,1428,
%U A173247 -1522,1619,-1719,1822,-1928,2037,-2149,2264,-2382,2503,-2627,2754
%N A173247 a(0) = -1 and a(n) = (-1)^n*(n - 4 - 3*n^2)/2 for n >= 1.
%H A173247 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-3,-3,-1).
%F A173247 G.f.: (x^3 - x^2 - 1)/(x + 1)^3.
%F A173247 a(n) = -3*a(n-1) -3*a(n-2) -a(n-3).
%F A173247 From _Franck Maminirina Ramaharo_, Dec 27 2018: (Start)
%F A173247 a(n) = (A143689(n) + 1)*(-1)^(n + 1), n >= 1.
%F A173247 E.g.f.: 1 - (1/2)*(4 - 2*x + 3*x^2)*exp(-x). (End)
%t A173247 p[x_] = (x^3 - x^2 - 1)/(x + 1)^3;
%t A173247 a = Table[SeriesCoefficient[ Series[p[x], {x, 0, 50}], n], {n, 0, 50}]
%o A173247 (Magma) [-1] cat [(-1)^n*(n-4-3*n^2)/2: n in [1..50]]; // _Vincenzo Librandi_, Apr 20 2015
%o A173247 (PARI) Vec((x^3 - x^2 - 1)/(x + 1)^3 + O(x^50)) \\ _Michel Marcus_, Apr 20 2015
%Y A173247 Cf. A089071, A105811, A143689.
%K A173247 sign,easy
%O A173247 0,2
%A A173247 _Roger L. Bagula_, Feb 13 2010
%E A173247 Definition simplified by the Assoc. Editors of the OEIS, Feb 21 2010
%E A173247 Incorrect comment removed by _Joerg Arndt_, Dec 27 2018