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 A137342 #8 Apr 01 2015 17:10:39 %S A137342 1,4,240,52032,37961472,95557604352,873176389545984, %T A137342 30234012628981334016,4073184753921806027390976, %U A137342 2164965110784257951109280432128,4571419424684923104187906920444592128 %N A137342 Number of rational series having complexity n over the finite field F_2 in two non-commuting variables. %H A137342 Roland Bacher, Apr 08 2008, <a href="/A137342/b137342.txt">Table of n, a(n) for n = 0..14</a> %H A137342 R. Bacher, <a href="http://arxiv.org/abs/0804.1092">The special subgroup of invertible non-commutative rational power series as a metric group</a>, arXiv:0804.1092 %F A137342 The reference contains a somewhat complicated formula. %K A137342 nonn %O A137342 0,2 %A A137342 _Roland Bacher_, Apr 08 2008