<Dl> <Dd> ∑ Ω (n) = 2 1 n 2 ≈ 0.1407604 (\ displaystyle \ sum _ (\ Omega (n) = 2) (\ frac (1) (n ^ (2))) \ approx 0.1407604) (sequence A117543 in the OEIS) </Dd> <Dd> ∑ Ω (n) = 2 1 n (n − 1) ≈ 0.17105 (\ displaystyle \ sum _ (\ Omega (n) = 2) (\ frac (1) (n (n - 1))) \ approx 0.17105) (sequence A152447 in the OEIS) </Dd> <Dd> ∑ Ω (n) = 2 ln ⁡ n n 2 ≈ 0.28360 (\ displaystyle \ sum _ (\ Omega (n) = 2) (\ frac (\ ln n) (n ^ (2))) \ approx 0.28360) (sequence A154928 in the OEIS) </Dd> </Dl> <Dd> ∑ Ω (n) = 2 1 n 2 ≈ 0.1407604 (\ displaystyle \ sum _ (\ Omega (n) = 2) (\ frac (1) (n ^ (2))) \ approx 0.1407604) (sequence A117543 in the OEIS) </Dd> <Dd> ∑ Ω (n) = 2 1 n (n − 1) ≈ 0.17105 (\ displaystyle \ sum _ (\ Omega (n) = 2) (\ frac (1) (n (n - 1))) \ approx 0.17105) (sequence A152447 in the OEIS) </Dd> <Dd> ∑ Ω (n) = 2 ln ⁡ n n 2 ≈ 0.28360 (\ displaystyle \ sum _ (\ Omega (n) = 2) (\ frac (\ ln n) (n ^ (2))) \ approx 0.28360) (sequence A154928 in the OEIS) </Dd>

Will the product of two prime numbers always be a prime number