Largest prime factor of 6^n - 1.

Terms

a(0) =5a(1) =7a(2) =43a(3) =37a(4) =311a(5) =43a(6) =55987a(7) =1297a(8) =2467a(9) =311a(10) =3154757a(11) =97a(12) =760891a(13) =55987a(14) =1201a(15) =98801a(16) =30839a(17) =46441a(18) =638073026189a(19) =6781a(20) =1822428931a(21) =51828151a(22) =7505944891a(23) =1678321a(24) =40185601a(25) =760891a(26) =623067280651a(27) =5030761a(29) =1950271