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 A260696 #32 Sep 08 2022 08:46:13
%S A260696 1,1,2,6,20,62,172,471,1337,3846,11030,31442,89470,254934,727203,
%T A260696 2074435,5915652,16866988,48093810,137141828,391072846,1115164897,
%U A260696 3179915535,9067592160,25856510664,73730732368,210245631360,599521974384,1709555338705,4874850377793,13900789573274,39638539791222
%N A260696 The number of length-n permutations avoiding the patterns 1234, 1324, 1432 and 3214.
%H A260696 C. Bean, M. Tannock and H. Ulfarsson, <a href="http://arxiv.org/abs/1512.08155">Pattern avoiding permutations and independent sets in graphs</a>, arXiv:1512.08155 [math.CO], 2015.
%H A260696 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (2,1,2,4,8,0,-15,-14,-7).
%F A260696 G.f.: -(x^3 + x^2 + x - 1)/(7*x^9 + 14*x^8 + 15*x^7 - 8*x^5 - 4*x^4 - 2*x^3 - x^2 - 2*x + 1).
%F A260696 a(n) = 2*a(n-1)+a(n-2)+2*a(n-3)+4*a(n-4)+8*a(n-5)-15*a(n-7)-14*a(n-8)-7*a(n-9) for n>8. - _Wesley Ivan Hurt_, Dec 29 2015
%t A260696 CoefficientList[Series[-(x^3 + x^2 + x - 1)/(7*x^9 + 14*x^8 + 15*x^7 - 8*x^5 - 4*x^4 - 2*x^3 - x^2 - 2*x + 1), {x, 0, 30}], x] (* _Wesley Ivan Hurt_, Dec 29 2015 *)
%t A260696 LinearRecurrence[{2, 1, 2, 4, 8, 0, -15, -14, -7}, {1, 1, 2, 6, 20, 62, 172, 471, 1337}, 40 ] (* _Vincenzo Librandi_, Dec 31 2015 *)
%o A260696 (Magma) I:=[1,1,2,6,20,62,172,471,1337]; [n le 9 select I[n] else 2*Self(n-1)+Self(n-2)+2*Self(n-3)+4*Self(n-4)+8*Self(n-5)-15*Self(n-7)-14*Self(n-8)-7*Self(n-9): n in [1..35]]; // _Vincenzo Librandi_, Dec 31 2015
%Y A260696 Cf. A263790.
%K A260696 nonn
%O A260696 0,3
%A A260696 _Christian Bean_, Nov 26 2015