%N Products of four primes, two of which are distinct.
%C Numbers with exactly four prime factors (counted with multiplicity) and exactly two distinct prime factors.
%C Numbers n such that bigomega(n) = 4 and omega(n) = 2.
%C Products of a prime and the cube of a different prime (pq^3) together with squares of squarefree semiprimes (p^2*q^2).
%t Select[Range@ 1050, And[PrimeNu@ # == 2, PrimeOmega@ # == 4] &] (* _Michael De Vlieger_, Apr 21 2019 *)
%o (Python 3)
%o import sympy
%o def bigomega(n): return sympy.primeomega(n)
%o def omega(n): return len(sympy.primefactors(n))
%o print([n for n in range(1, 1000) if bigomega(n) == 4 and omega(n) == 2])
%o (PARI) isok(n) = (bigomega(n) == 4) && (omega(n) == 2); \\ _Michel Marcus_, Apr 22 2019
%Y Union of A065036 and A085986.
%Y Intersection of A007774 and A067801.
%Y Intersection of A007774 and A195086.
%Y Intersection of A014613 and A067801.
%Y Intersection of A014613 and A195086.
%Y Cf. A307342.
%A _Kalle Siukola_, Apr 21 2019