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%I #6 Dec 12 2024 11:09:09
%S 0,1,1,1,0,1,0,1,1,0,0,1,1,0,0,1,0,1,0,1,0,0,0,1,0,0,1,0,1,0,1,0,1,0,
%T 0,0,1,1,0,0,0,1,0,0,1,1,0,0,0,1,0,1,0,0,0,1,0,0,0,0,1,1,0,1,0,0,1,1,
%U 0,0,1,0,0,0,0
%N a(n) = 0 if s(n) is nonprime, a(n) = 1 if s(n) is prime, where s = A005117.
%C Characteristic function of prime squarefree numbers.
%C First differences of pi(s(n)) = A000720(A005117(n)).
%H Michael De Vlieger, <a href="/A378901/b378901.txt">Table of n, a(n) for n = 1..10000</a>
%F a(k) = 1 for k in A071403.
%t Map[Boole[PrimeQ[#]] &, Select[Range[120], SquareFreeQ] ]
%Y Cf. A000040, A000720, A005117, A071403.
%K nonn,easy,new
%O 1
%A _Michael De Vlieger_, Dec 12 2024