a(n) is the largest prime factor in A030426(n).

Terms

a(0) =2a(1) =5a(2) =13a(3) =89a(4) =233a(5) =1597a(6) =113a(7) =28657a(8) =514229a(9) =2417a(10) =2221a(11) =59369a(12) =433494437a(13) =2971215073a(14) =55945741a(15) =2710260697a(16) =555003497a(17) =1429913a(18) =46165371073a(19) =86020717a(23) =361040209a(24) =770857978613a(25) =512119709