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 A111283 #29 Aug 04 2025 12:18:28
%S A111283 1,1,2,6,23,96,409,1751,7505,32176,137956,591501,2536132,10873981,
%T A111283 46623553,199904321,857114814,3674987126,15756967635,67559972476,
%U A111283 289671844661,1242004318751,5325249092137,22832672531956,97897943538708
%N A111283 Number of permutations avoiding the patterns {4321, 45132, 45231, 35412, 53412, 45213, 43512, 45312, 456123, 451623, 356124}; number of strong sorting class based on 4321.
%H A111283 M. Albert, R. Aldred, M. Atkinson, C Handley, D. Holton, D. McCaughan and H. van Ditmarsch, <a href="https://doi.org/10.37236/1928">Sorting Classes</a>, Elec. J. of Comb., Vol. 12 (2005), R31.
%H A111283 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (5,-3,0,-1).
%F A111283 a(n) = 4*a(n-1) + a(n-2) + a(n-3) - 4; n>=4.
%F A111283 G.f.: 1+x*(1-3*x-x^2-x^3)/((1-x)*(1-4*x-x^2-x^3)). - _Colin Barker_, Jan 16 2012
%F A111283 a(n) = 5*a(n-1) - 3*a(n-2) - a(n-4). - _Wesley Ivan Hurt_, Aug 04 2025
%t A111283 a[1] = 1; a[2] = 2; a[3] = 6; a[n_] := a[n] = 4a[n - 1] + a[n - 2] + a[n - 3] - 4; Table[a[n], {n, 24}] (* _Robert G. Wilson v_, Nov 04 2005 *)
%t A111283 LinearRecurrence[{5,-3,0,-1},{1,2,6,23},30] (* _Harvey P. Dale_, Jan 01 2017 *)
%K A111283 nonn
%O A111283 0,3
%A A111283 _Len Smiley_, Nov 01 2005
%E A111283 More terms from _Robert G. Wilson v_, Nov 04 2005
%E A111283 a(0)=1 prepended by _Alois P. Heinz_, Mar 12 2024