a(1) = 1; for n > 1, a(n) = largest prime divisor of A062273(n).

Terms

a(0) =1a(1) =23a(2) =19a(3) =263a(4) =823a(5) =678901a(6) =50993a(7) =1279a(8) =211a(9) =150866941a(10) =353594393a(11) =757819a(13) =213408443a(14) =11904282563a(15) =435503a(16) =21339439879a(17) =7403356241a(19) =27961a(20) =205126079a(24) =12792129877