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%I #5 Jan 16 2024 11:53:41
%S 0,0,0,0,1,1,2,1,2,3,4,2,4,4,5,5,6,4,6,4,6,7,8,6,8,9,9,8,10,7,10,9,10,
%T 11,12,10,13,13,14,13,15,12,15,13,13,15,16,14,16,15,17,16,18,16,18,17,
%U 19,20,21,17,21,21,20,21,22,20,23,21,23,21,24,21,24,24,23
%N Number of semiprimes less than n that do not divide n.
%F a(n) = Sum_{k=1..n} c(k) * (ceiling(n/k) - floor(n/k)), where c = A064911.
%t Table[Sum[KroneckerDelta[PrimeOmega[k], 2] (Ceiling[n/k] - Floor[n/k]), {k, n}], {n, 100}]
%Y Cf. A001358 (semiprimes), A064911, A369225.
%K nonn,easy
%O 1,7
%A _Wesley Ivan Hurt_, Jan 16 2024
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