Numbers of the form p^2*q^2*r*s where p, q, r, and s are distinct primes.

Terms

a(0) =1260a(1) =1980a(2) =2100a(3) =2340a(4) =2772a(5) =2940a(6) =3060a(7) =3150a(8) =3276a(9) =3300a(10) =3420a(11) =3900a(12) =4140a(13) =4284a(14) =4410a(15) =4788a(16) =4950a(17) =5100a(18) =5148a(19) =5220a(20) =5580a(21) =5700a(22) =5796a(23) =5850a(24) =6468a(25) =6660a(26) =6732a(27) =6900a(28) =7260a(29) =7308