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 A058051 #16 Feb 09 2018 19:42:40
%S A058051 0,1,1,1,1,5,10946,2211236406303914545699412969744873993387956988653
%N A058051 a(n) = F(F(F(n))), where F is a Fibonacci number (A000045).
%C A058051 a(8) = 1695216512..7257812353 has 2288 decimal digits and a(9) = 3525796792..4659808333 has 1191833 decimal digits. - _Alois P. Heinz_, Nov 11 2015
%p A058051 F:= n-> (<<0|1>, <1|1>>^n)[1, 2]:
%p A058051 a:= n-> F(F(F(n))):
%p A058051 seq(a(n), n=0..7); # _Alois P. Heinz_, Nov 11 2015
%t A058051 F[0] = 0; F[1] = 1; F[n_] := F[n] = F[n - 1] + F[n - 2]; Table[ F[ F[ F[n] ] ], {n, 0, 10} ]
%t A058051 Table[Nest[Fibonacci,n,3],{n,0,8}] (* _Harvey P. Dale_, Feb 09 2018 *)
%Y A058051 Cf. A000045, A007570, A262361.
%K A058051 easy,nonn
%O A058051 0,6
%A A058051 _Robert G. Wilson v_, Nov 18 2000
%E A058051 Offset corrected by _Alois P. Heinz_, Nov 11 2015