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A346623 a(n) = Sum_{ x <= n : x odd and omega(x) = 2 } x.

%I A346623 #17 Feb 13 2023 05:16:57
%S A346623 0,0,0,0,0,0,0,0,0,0,0,0,0,0,15,15,15,15,15,15,36,36,36,36,36,36,36,
%T A346623 36,36,36,36,36,69,69,104,104,104,104,143,143,143,143,143,143,188,188,
%U A346623 188,188,188,188,239,239,239,239,294,294,351,351,351,351,351,351,414,414,479,479,479,479
%N A346623 a(n) = Sum_{ x <= n : x odd and omega(x) = 2 } x.
%H A346623 Alois P. Heinz, <a href="/A346623/b346623.txt">Table of n, a(n) for n = 1..20000</a>
%p A346623 a:= proc(n) option remember; `if`(n=0, 0, a(n-1)+
%p A346623      `if`(n::odd and nops(ifactors(n)[2])=2, n, 0))
%p A346623     end:
%p A346623 seq(a(n), n=1..68);  # _Alois P. Heinz_, Aug 23 2021
%t A346623 a[n_] := a[n] = If[n == 1, 0, a[n-1] + If[OddQ[n] && PrimeNu[n] == 2, n, 0]];
%t A346623 Table[a[n], {n, 1, 100}] (* _Jean-François Alcover_, Feb 13 2023 *)
%o A346623 (Python)
%o A346623 from sympy import primefactors
%o A346623 def A346623(n):
%o A346623     return 0 if n <= 2 else A346623(n-1) + (n if n % 2 and len(primefactors(n)) == 2 else 0) # _Chai Wah Wu_, Aug 23 2021
%Y A346623 Cf. A001221, A007774, A346221, A346222.
%K A346623 nonn
%O A346623 1,15
%A A346623 _N. J. A. Sloane_, Aug 23 2021