This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A307682 #15 Nov 13 2024 16:34:01 %S A307682 24,36,40,54,56,88,100,104,135,136,152,184,189,196,225,232,248,250, %T A307682 296,297,328,344,351,375,376,424,441,459,472,484,488,513,536,568,584, %U A307682 621,632,664,676,686,712,776,783,808,824,837,856,872,875,904,999,1016,1029 %N A307682 Products of four primes, two of which are distinct. %C A307682 Numbers with exactly four prime factors (counted with multiplicity) and exactly two distinct prime factors. %C A307682 Numbers n such that bigomega(n) = 4 and omega(n) = 2. %C A307682 Products of a prime and the cube of a different prime (pq^3) together with squares of squarefree semiprimes (p^2*q^2). %t A307682 Select[Range@ 1050, And[PrimeNu@ # == 2, PrimeOmega@ # == 4] &] (* _Michael De Vlieger_, Apr 21 2019 *) %o A307682 (Python) %o A307682 import sympy %o A307682 def bigomega(n): return sympy.primeomega(n) %o A307682 def omega(n): return len(sympy.primefactors(n)) %o A307682 print([n for n in range(1, 1000) if bigomega(n) == 4 and omega(n) == 2]) %o A307682 (PARI) isok(n) = (bigomega(n) == 4) && (omega(n) == 2); \\ _Michel Marcus_, Apr 22 2019 %Y A307682 Union of A065036 and A085986. %Y A307682 Intersection of A007774 and A067801. %Y A307682 Intersection of A007774 and A195086. %Y A307682 Intersection of A014613 and A067801. %Y A307682 Intersection of A014613 and A195086. %Y A307682 Cf. A307342. %K A307682 nonn %O A307682 1,1 %A A307682 _Kalle Siukola_, Apr 21 2019