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A318841 a(n) = n - A173557(n).

%I A318841 #11 Dec 16 2023 09:01:15
%S A318841 0,1,1,3,1,4,1,7,7,6,1,10,1,8,7,15,1,16,1,16,9,12,1,22,21,14,25,22,1,
%T A318841 22,1,31,13,18,11,34,1,20,15,36,1,30,1,34,37,24,1,46,43,46,19,40,1,52,
%U A318841 15,50,21,30,1,52,1,32,51,63,17,46,1,52,25,46,1,70,1,38,67,58,17,54,1,76,79,42,1,72,21,44,31,78,1,82,19,70,33,48
%N A318841 a(n) = n - A173557(n).
%H A318841 Antti Karttunen, <a href="/A318841/b318841.txt">Table of n, a(n) for n = 1..65537</a>
%F A318841 a(n) = n - A173557(n).
%F A318841 Sum_{k=1..n} a(k) ~ c * n^2 / 2, where c = 1 - A307868 = 0.528319... . - _Amiram Eldar_, Dec 16 2023
%t A318841 a[n_] := n - Times @@ (FactorInteger[n][[;;, 1]] - 1); a[1] = 0; Array[a, 100] (* _Amiram Eldar_, Dec 16 2023 *)
%o A318841 (PARI)
%o A318841 A173557(n) = factorback(apply(p -> p-1, factor(n)[, 1]));
%o A318841 A318841(n) = (n-A173557(n));
%Y A318841 Cf. A173557, A307868, A318833.
%K A318841 nonn,easy
%O A318841 1,4
%A A318841 _Antti Karttunen_, Sep 16 2018