First semiprime after e^n.

Terms

a(0) =4a(1) =4a(2) =9a(3) =21a(4) =55a(5) =155a(6) =407a(7) =1099a(8) =2981a(9) =8105a(10) =22033a(11) =59881a(12) =162757a(13) =442417a(14) =1202611a(15) =3269021a(16) =8886117a(17) =24154953a(18) =65659981a(19) =178482301a(20) =485165203a(21) =1318815739a(22) =3584912849a(23) =9744803447a(24) =26489122131a(25) =72004899341a(26) =195729609431