%I #6 Jun 12 2021 22:12:17
%S 0,2,1,2,5,3,1,2,1,7,11,3,1,3,6,2,17,3,1,7,2,13,23,3,5,3,1,3,1,8,31,2,
%T 12,19,6,3,1,3,2,7,41,4,1,13,6,25,47,3,1,7,18,3,1,3,16,3,2,3,59,8,1,
%U 33,2,2,6,14,67,19,24,8,1,3,73,3,6,3,12,4,1,7,1,43,83,4,22,3
%N a(n) = Sum_{p|n} p^(pi(p) mod 2).
%e a(15) = Sum_{p|15} p^(pi(p) mod 2) = 3^0 + 5^1 = 6.
%t Table[Sum[k^Mod[PrimePi[k], 2] (PrimePi[k] - PrimePi[k - 1]) (1 - Ceiling[n/k] + Floor[n/k]), {k, n}], {n, 100}]
%Y Cf. A000720 (pi), A345279.
%K nonn
%O 1,2
%A _Wesley Ivan Hurt_, Jun 12 2021