Semiprimes in A006053.

Terms

a(0) =4a(1) =9a(2) =14a(3) =155a(4) =2993a(5) =9707a(6) =184183a(7) =331981a(8) =1942071a(9) =1263047761a(10) =140390505643a(11) =455845099957