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 A037898 #8 Feb 19 2020 13:42:40
%S A037898 0,0,0,1,0,1,2,2,1,0,1,3,2,1,0,1,1,2,3,1,0,1,2,2,1,1,2,3,2,2,2,2,2,2,
%T A037898 3,2,1,1,2,2,1,0,1,3,2,1,1,3,3,3,3,3,2,2,2,3,2,1,1,3,2,1,0,1,1,2,3,1,
%U A037898 1,2,3,2,2,2,3,3,3,3,3,1,1,2,3,1,0,1,2,2,1,1
%N A037898 a(n)=(greatest base 4 digit of n)-(least base 4 digit of n).
%p A037898 A037898 := proc(n)
%p A037898 local dgs ;
%p A037898 dgs := convert(n,base,4);
%p A037898 max(op(dgs))-min(op(dgs)) ;
%p A037898 end proc: # _R. J. Mathar_, Oct 19 2015
%t A037898 gb4[n_]:=Module[{idn4=IntegerDigits[n,4]},Max[idn4]-Min[idn4]]; Array[ gb4,120] (* _Harvey P. Dale_, Feb 19 2020 *)
%K A037898 nonn,base
%O A037898 1,7
%A A037898 _Clark Kimberling_