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a(n) = Sum_{k=1..n} pi(k) * floor(n/k).
5

%I #7 Jan 01 2024 22:28:27

%S 0,1,3,6,9,15,19,26,32,40,45,58,64,75,86,99,106,123,131,149,163,177,

%T 186,212,224,240,255,277,287,316,327,351,369,388,406,441,453,474,494,

%U 528,541,578,592,622,651,675,690,737,756,788,812,845,861,903,927,969,995,1022

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

%F a(n) = A013939(n) + A368613(n).

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

%Y Cf. A000720 (pi), A013939, A046992, A368610, A368612, A368613.

%K nonn,easy

%O 1,3

%A _Wesley Ivan Hurt_, Dec 31 2023