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 A040174 #14 Feb 16 2025 08:32:38 %S A040174 1,4,2,8,40,120,168,6720,120960,44800,6652800,14515200,415134720 %N A040174 Denominator of probability that 2 elements of S_n chosen at random (with replacement) generate S_n. %H A040174 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SymmetricGroup.html">Symmetric Group.</a> %e A040174 Values for n=1,2,3,... are 1, 3/4, 1/2, 3/8, 19/40, 53/120, 103/168, 4111/6720, 78293/120960, ... %Y A040174 Probability is A040173/A040174 = A040175/n!. %K A040174 nonn,frac,nice,more %O A040174 1,2 %A A040174 _Dan Hoey_ %E A040174 a(10)-a(13) from _Stephen A. Silver_, Feb 21 2013