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 A253207 #9 Jun 13 2015 00:55:20 %S A253207 11,59,359,1799,7091,22995,64143,159093,359348,752180,1478204,2754752, %T A253207 4906202,8402522,13907394,22337388,34933761,53348561,79746821, %U A253207 116926733,168459797,238853045,333735545,460071495,626402322,843120306,1122776354 %N A253207 a(n) = number of permutations of (1,2,...,n) producible by an ordered quadruple of distinct transpositions. %H A253207 Colin Barker, <a href="/A253207/b253207.txt">Table of n, a(n) for n = 4..1000</a> %H A253207 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (9,-36,84,-126,126,-84,36,-9,1). %F A253207 a(n) = n!*(1/(384*(n-8)!)+1/(24*(n-7)!)+13/(72*(n-6)!)+1/(5*(n-5)!)+1/(8*(n-4)!)+1/(3*(n-3)!)) for n>=8. %o A253207 (PARI) Vec(-x^4*(2*x^8-18*x^7+72*x^6-168*x^5+254*x^4-232*x^3+224*x^2-40*x+11)/(x-1)^9 + O(x^100)) \\ _Colin Barker_, Dec 30 2014 %Y A253207 Cf. A000914, for two transpositions, and A253171, for three. %K A253207 nonn,easy %O A253207 4,1 %A A253207 _Andrew Woods_, Dec 28 2014