Least number having exactly two odd prime factors that differ by 2^n.

Terms

a(0) =15a(1) =21a(2) =33a(3) =57a(4) =185a(5) =201a(6) =393a(7) =1841a(8) =5753a(9) =7217a(10) =10265a(11) =12297a(12) =139553a(13) =607577a(14) =98313a(15) =196617a(16) =3801929a(17) =786441a(18) =27790073a(19) =7340081a(20) =35651873a(21) =281022857a(22) =92274809a(23) =721422137a(24) =1375733393a(25) =6509569217a(26) =3892314953a(27) =805306377