This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A084963 #12 Sep 29 2023 19:14:26
%S A084963 7,13,233,2211236406303914545699412969744873993387956988653
%N A084963 a(0) = 7, a(n+1) = Fibonacci(a(n)).
%C A084963 Iteration of the Fibonacci sequence.
%C A084963 a(3) = 2.2112... * 10^48.
%e A084963 a(2) = F(a(1)) = F(13) = 233.
%p A084963 a:= proc(n) option remember; `if`(n=0, 7,
%p A084963 (<<0|1>, <1|1>>^a(n-1))[1,2])
%p A084963 end:
%p A084963 seq(a(n), n=0..3); # _Alois P. Heinz_, May 09 2020
%t A084963 a[m_] := Module[{ex = 7}, Do[ex = Fibonacci[ex], {m}]; ex] Table[a[m], {m, 0, 3}]
%t A084963 NestList[Fibonacci[#]&,7,3] (* _Harvey P. Dale_, Mar 18 2018 *)
%Y A084963 Cf. A000045, A084962.
%K A084963 nonn
%O A084963 0,1
%A A084963 _Hollie L. Buchanan II_, Jun 14 2003