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%I #6 Jan 01 2024 21:55:12
%S 0,0,1,1,1,1,1,0,0,1,1,0,1,1,1,1,1,0,1,1,1,1,1,0,1,1,1,1,1,1,1,1,1,1,
%T 1,0,1,1,1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,0,1,1,1,1,1,1,1,1,
%U 1,1,1,0,1,1,1,1,1,1,1,0,1,1,1,0,1,1,1,0,1,1,1,1,1,1,1,0,1
%N Characteristic function of non-refactorable numbers (A159973).
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/RefactorableNumber.html">Refactorable Number</a>
%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%F a(n) = ceiling(n/d(n))-floor(n/d(n)), where d(n) is the number of divisors of n (A000005).
%F a(n) = 1 - A336040(n).
%t Table[(Ceiling[n/DivisorSigma[0, n]] - Floor[n/DivisorSigma[0, n]]), {n, 100}]
%Y Cf. A000005, A033950 (refactorable numbers), A159973, A336040.
%K nonn,easy
%O 1,1
%A _Wesley Ivan Hurt_, Jan 01 2024
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