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 A075099 #7 Jul 12 2015 20:34:21 %S A075099 0,4,11,20,42,75 %N A075099 Minimal total number of multiplications needed to generate all words of length n in the free monoid on two generators. %C A075099 _Benoit Jubin_ (Jan 24 2009) suggests replacing "monoid" in the definition by "semigroup". %C A075099 I believe a(2n) = a(n) + 2^(2n). I guess a(7) = 156. %e A075099 a(3)=11 because each of xxx,xxy,xyx,xyy,yxx,yxy,yyx,yyy can be obtained in one step from xx,xy,yy and it takes three multiplications to produce xx, xy, yy. %Y A075099 Cf. A075100, A124677 (another version). %K A075099 hard,more,nonn %O A075099 1,2 %A A075099 _Colin Mallows_, Aug 31 2002