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 A050108 #12 Oct 05 2019 18:22:29
%S A050108 1,5,25,6,30,7,35,8,2,10,50,12,3,15,75,18,4,20,100,500,125,31,155,38,
%T A050108 9,45,11,55,13,65,16,80,400,2000,10000,2500,625,156,39,195,48,240,60,
%U A050108 300,1500,375,93,23,115,28,140,700,175,43,215
%N A050108 a(n) = floor(a(n-1)/4) if this is positive and not yet in the sequence, otherwise a(n) = 5*a(n-1).
%H A050108 Ivan Neretin, <a href="/A050108/b050108.txt">Table of n, a(n) for n = 1..10000</a>
%t A050108 Rest@Nest[Append[#, If[FreeQ[#, r = Quotient[#[[-1]], 4]], r, 5 #[[-1]]]] &, {0, 1}, 55] (* _Ivan Neretin_, Jul 31 2016 *)
%o A050108 (PARI) first(n)=my(v=vector(n),t); v[1]=1; for(i=2,n, t=v[i-1]\4; if(t<2, v[i]=5*v[i-1]; next); for(j=1,i-1, if(v[j]==t, v[i]=5*v[i-1]; next(2))); v[i]=t); v \\ _Charles R Greathouse IV_, Jul 31 2016
%Y A050108 Cf. A050000 and references therein.
%K A050108 nonn
%O A050108 1,2
%A A050108 _Clark Kimberling_