Odd numbers having no odd primes in their Collatz (3x+1) trajectory.

Terms

a(0) =1a(1) =21a(2) =85a(3) =341a(4) =453a(5) =909a(6) =1365a(7) =1813a(8) =5461a(9) =7281a(10) =9669a(11) =21845a(12) =29013a(13) =29125a(14) =38835a(15) =45839a(16) =54327a(17) =58197a(18) =58253a(19) =68759a(20) =77667a(21) =81491a(22) =87381a(23) =103139a(24) =116053a(25) =116501a(26) =122237a(27) =154709a(28) =154737a(29) =155341