Numbers whose prime factors are 3 and 7.

Terms

a(0) =21a(1) =63a(2) =147a(3) =189a(4) =441a(5) =567a(6) =1029a(7) =1323a(8) =1701a(9) =3087a(10) =3969a(11) =5103a(12) =7203a(13) =9261a(14) =11907a(15) =15309a(16) =21609a(17) =27783a(18) =35721a(19) =45927a(20) =50421a(21) =64827a(22) =83349a(23) =107163a(24) =137781a(25) =151263a(26) =194481a(27) =250047a(28) =321489a(29) =352947