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 A091219 #11 Jul 10 2015 19:34:28 %S A091219 1,-1,-1,0,0,1,-1,0,1,0,-1,0,-1,1,0,0,0,-1,-1,0,0,1,1,0,-1,1,0,0,1,0, %T A091219 -1,0,1,0,1,0,-1,1,0,0,-1,0,1,0,0,-1,-1,0,1,1,0,0,1,0,-1,0,0,-1,-1,0, %U A091219 -1,1,0,0,0,-1,-1,0,0,-1,1,0,-1,1,0,0,1,0,1,0,0,1,-1,0,0,-1,-1,0,1,0 %N A091219 Moebius-analog for the domain GF(2)[X]: a(n)=0 if A091221(n)!=A091222(n) (i.e., if the polynomial is not squarefree), otherwise (-1)^A091222(n). %C A091219 The absolute values give a characteristic function for squarefree GF(2)[X]-polynomials. %H A091219 A. Karttunen, <a href="/A091247/a091247.scm.txt">Scheme-program for computing this sequence.</a> %H A091219 <a href="/index/Ge#GF2X">Index entries for sequences operating on GF(2)[X]-polynomials</a> %Y A091219 a(n) = A008683(A091203(n)) = A008683(A091205(n)). %K A091219 sign %O A091219 1,1 %A A091219 _Antti Karttunen_, Jan 03 2004