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%I #18 Jan 14 2024 00:15:23
%S 0,0,1,1,2,2,3,3,4,4,5,5,6,6,6,6,7,7,8,8,8,8,9,9,10,10,11,11,12,12,13,
%T 13,13,13,13,13,14,14,14,14,15,15,16,16,16,16,17,17,18,18,18,18,19,19,
%U 19,19,19,19,20,20,21,21,21,21,21,21,22,22,22,22,23,23,24,24,24
%N Number of odd prime powers <= n (with exponents > 0).
%F a(n) = A025528(n) - A000523(n).
%t Table[Sum[Boole[OddQ[k] && PrimePowerQ[k]], {k, 1, n}], {n, 1, 75}]
%o (PARI) a(n) = {sum(k=2, primepi(n), logint(n, prime(k)))} \\ _Andrew Howroyd_, Sep 14 2019
%Y Cf. A000523, A025528, A033270, A061345, A065515, A069637, A085501, A174275 (first differences), A246655, A285879.
%K nonn
%O 1,5
%A _Ilya Gutkovskiy_, Sep 14 2019