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 A106743 #11 May 21 2017 18:27:47
%S A106743 0,-1,-1,1,-1,0,-1,1,1,0,-1,1,-1,0,0,1,-1,1,-1,1,0,0,-1,1,1,0,1,1,-1,
%T A106743 0,-1,1,0,0,0,1,-1,0,0,1,-1,0,-1,1,1,0,-1,1,1,1,0,1,-1,1,0,1,0,0,-1,1,
%U A106743 -1,0,1,1,0,0,-1,1,0,0,-1,1,-1,0,1,1,0,0,-1,1,1,0,-1,1,0,0,0,1,-1,1,0,1,0,0,0,1,-1,1,1,1,-1,0,-1,1,0
%N A106743 a(n) = -1 iff n is prime, a(n) = 1 iff n is not squarefree, otherwise (n is nonprime and squarefree) a(n) = 0.
%H A106743 G. C. Greubel, <a href="/A106743/b106743.txt">Table of n, a(n) for n = 1..1000</a>
%F A106743 a(n) = 1 - 0^(A001222(n)-A001221(n)) - 0^(A001222(n)-1), for n>1. - _Reinhard Zumkeller_, May 23 2005
%t A106743 Table[Which[PrimeQ[n],-1,SquareFreeQ[n],0,True,1],{n,110}] (* _Harvey P. Dale_, Aug 30 2015 *)
%o A106743 (PARI) for(n=1,105,print1(if(!issquarefree(n),1,if(isprime(n),-1,0)),","))
%Y A106743 Cf. A000040 (prime), A013929 (not squarefree), A000469 (nonprime and squarefree), A082926.
%K A106743 sign
%O A106743 1,1
%A A106743 _Giovanni Teofilatto_, May 16 2005
%E A106743 Edited and extended by _Klaus Brockhaus_, May 16 2005