A106743 - OEIS

%I #11 May 21 2017 18:27:47

%S 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 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 -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 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 G. C. Greubel, <a href="/A106743/b106743.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = 1 - 0^(A001222(n)-A001221(n)) - 0^(A001222(n)-1), for n>1. - _Reinhard Zumkeller_, May 23 2005

%t Table[Which[PrimeQ[n],-1,SquareFreeQ[n],0,True,1],{n,110}] (* _Harvey P. Dale_, Aug 30 2015 *)

%o (PARI) for(n=1,105,print1(if(!issquarefree(n),1,if(isprime(n),-1,0)),","))

%Y Cf. A000040 (prime), A013929 (not squarefree), A000469 (nonprime and squarefree), A082926.

%K sign

%O 1,1

%A _Giovanni Teofilatto_, May 16 2005

%E Edited and extended by _Klaus Brockhaus_, May 16 2005