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 A111286 #35 Mar 12 2024 21:21:31
%S A111286 1,1,2,6,12,24,48,96,192,384,768,1536,3072,6144,12288,24576,49152,
%T A111286 98304,196608,393216,786432,1572864,3145728,6291456,12582912,25165824,
%U A111286 50331648,100663296,201326592,402653184,805306368,1610612736,3221225472
%N A111286 Number of permutations avoiding the patterns {1342, 1432, 2341, 2431, 3142, 3241, 3412, 3421, 4132, 4231, 4312, 4321}; number of strong sorting class based on 1342.
%H A111286 Vincenzo Librandi, <a href="/A111286/b111286.txt">Table of n, a(n) for n = 0..1000</a>
%H A111286 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 A111286 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (2).
%F A111286 a(n) = 3*2^(n-2), n>=3.
%F A111286 a(n) = 2*a(n-1) for n=3. G.f.: (1-x+2*x^3)/(1-2*x). - _Colin Barker_, Nov 29 2012
%t A111286 Table[If[n == 1, 1, If[n == 2, 2, 3*2^(n - 2)]], {n, 32}] (* _Robert G. Wilson v_ *)
%t A111286 LinearRecurrence[{2},{1,2,6},40] (* _Harvey P. Dale_, Jul 14 2019 *)
%Y A111286 Cf. A003945, A007283, A042950, A098011, A110164 - differs from each by one initial term.
%K A111286 nonn,easy
%O A111286 0,3
%A A111286 _Len Smiley_, Nov 01 2005
%E A111286 a(0)=1 prepended by _Alois P. Heinz_, Mar 12 2024