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a(n) = Sum_{k=2..n} pi(k-1) * floor(n/k).
4

%I #8 Jan 01 2024 22:28:38

%S 0,0,1,3,5,9,12,18,23,29,33,44,49,58,67,79,85,100,107,123,135,147,155,

%T 179,190,204,218,238,247,273,283,306,322,339,355,388,399,418,436,468,

%U 480,514,527,555,582,604,618,663,681,711,733,764,779,819,841,881,905,930

%N a(n) = Sum_{k=2..n} pi(k-1) * floor(n/k).

%F a(n) = A368611(n) - A013939(n).

%t Table[Sum[PrimePi[k - 1] Floor[n/k], {k, 2, n}], {n, 100}]

%Y Cf. A000720 (pi), A013939, A046992, A368610, A368611, A368612.

%K nonn,easy

%O 1,4

%A _Wesley Ivan Hurt_, Dec 31 2023