Becomes prime after n iterations of f(x) = phi(x)+1 (least inverse of A039651).

Terms

a(0) =2a(1) =1a(2) =15a(3) =35a(4) =69a(5) =255a(6) =535a(7) =949a(8) =1957a(9) =2513a(10) =2923a(11) =4531a(12) =17701a(13) =22957a(14) =54589a(15) =79421a(16) =80029a(17) =84493a(18) =98581a(19) =102827a(20) =115243a(21) =239111a(22) =291149a(23) =310813a(24) =362621a(25) =398893a(26) =598341a(27) =801923a(28) =838307a(29) =1063493