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 A228393 #28 Jan 04 2017 14:11:07
%S A228393 1,2,6,24,120,675,3527,15484,56917,179719,500864,1260117,2913132,
%T A228393 6274230,12726573,24521243,45190897,80108200,137224138,228026582,
%U A228393 368765112,581994117,898492563,1359625566,2020220021,2952034021,4247907652,6026690971,8439053564
%N A228393 The number of permutations of length n that can be sorted by 3 block transpositions.
%H A228393 V. Bafna and P.A. Pevzner, <a href="http://dx.doi.org/10.1137/S089548019528280X">Sorting by transpositions</a>, SIAM J. Discrete Math. 11, 2 (1998), 224-240.
%H A228393 Cheyne Homberger, <a href="http://arxiv.org/abs/1410.2657">Patterns in Permutations and Involutions: A Structural and Enumerative Approach</a>, arXiv:1410.2657 [math.CO], 2014.
%H A228393 C. Homberger, V. Vatter, <a href="http://arxiv.org/abs/1308.4946">On the effective and automatic enumeration of polynomial permutation classes</a>, arXiv:1308.4946 [math.CO], 2013.
%H A228393 <a href="/index/Rec#order_10">Index entries for linear recurrences with constant coefficients</a>, signature (10,-45,120,-210,252,-210,120,-45,10,-1).
%F A228393 G.f.: -x*(x^9 - 9*x^8 - 17*x^7 - 263*x^6 - 3*x^5 - 120*x^4 + 66*x^3 - 31*x^2 + 8*x - 1)/(x - 1)^10.
%e A228393 The shortest permutations which cannot be sorted by 3 block transpositions are of length 6.
%t A228393 CoefficientList[Series[-(x^9 - 9 x^8 - 17 x^7 - 263 x^6 - 3 x^5 - 120 x^4 + 66 x^3 - 31 x^2 + 8 x - 1)/(x - 1)^10, {x, 0, 40}], x] (* _Bruno Berselli_, Aug 22 2013 *)
%Y A228393 Cf. A000292, A228392.
%K A228393 nonn,easy
%O A228393 1,2
%A A228393 _Vincent Vatter_, Aug 21 2013