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

Terms

a(0) =1a(1) =7a(2) =23a(3) =7a(4) =53a(5) =383a(6) =179a(7) =89a(8) =271a(9) =3413a(10) =2503a(11) =2137a(12) =59a(13) =367a(14) =1433a(15) =41a(16) =15803a(17) =59729a(18) =26423a(19) =11161a(20) =1559a(21) =12611a(22) =9187523a(23) =127867a(24) =119837257a(25) =11527a(26) =2360833a(27) =43969a(28) =2339a(29) =32212254719