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 A140343 #11 Jun 13 2015 00:52:38
%S A140343 0,0,0,0,1,4,9,14,14,0,-41,-122,-243,-364,-364,0,1093,3280,6561,9842,
%T A140343 9842,0,-29525,-88574,-177147,-265720,-265720,0,797161,2391484,
%U A140343 4782969,7174454,7174454,0,-21523361,-64570082,-129140163,-193710244,-193710244,0,581130733
%N A140343 a(n)=4a(n-1)-7a(n-2)+6a(n-3)-3a(n-4), n>4.
%C A140343 This is the main sequence representing the degenerate case of sequences which equal their sixth differences, where, besides the generic a(n)=6a(n-1)-15a(n-2)+20a(n-3)-15a(n-4)+6a(n-5), cf. A135356, there is also a shorter recurrence. Another sequence of this kind is A134581.
%H A140343 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-7,6,-3).
%F A140343 O.g.f.: x^4/((x^2-x+1)(3x^2-3x+1)). - _R. J. Mathar_, Jul 10 2008
%t A140343 Join[{0},LinearRecurrence[{4,-7,6,-3},{0,0,0,1},40]] (* _Harvey P. Dale_, Mar 11 2015 *)
%Y A140343 Cf. A135356.
%K A140343 sign,easy
%O A140343 0,6
%A A140343 _Paul Curtz_, May 29 2008
%E A140343 Edited and corrected by _R. J. Mathar_, Jul 10 2008