a(n) is the largest prime factor of 2^(prime(n) - 1) - 1.

Terms

a(0) =3a(1) =5a(2) =7a(3) =31a(4) =13a(5) =257a(6) =73a(7) =683a(8) =127a(9) =331a(10) =109a(11) =61681a(12) =5419a(13) =2796203a(14) =8191a(15) =3033169a(16) =1321a(17) =599479a(18) =122921a(19) =38737a(20) =22366891a(21) =8831418697a(22) =2931542417a(23) =22253377a(24) =268501a(25) =131071a(27) =279073a(28) =54410972897a(29) =77158673929