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 A081170 #4 Oct 01 2013 17:57:36
%S A081170 3,0,4,2,1,5,2,1,6,3,0,7,4,2,1,8,4,2,1,9,6,3,0,10,5,2,1,11,8,4,2,1,12,
%T A081170 6,3,0,13,10,5,2,1,14,7,4,2,1,15,12,6,3,0,16,8,4,2,1,17,14,7,4,2,1,18,
%U A081170 9,6,3,0,19,16,8,4,2,1,20,10,5,2,1,21,18,9,6,3,0,22,11,8,4,2,1,23,20,10,5,2
%N A081170 Triangle in which n-th row gives trajectory of n (including n itself) under the map x -> x/2 if x is even, x -> x-3 if x is odd, stopping when reach 0 or 1.
%o A081170 (PARI) xn1m3(n) = { for(x=3,n, x1=x; print1(x1" "); while(x1>1, if(x1%2==0,x1/=2,x1=x1-3); print1(x1" "); ) ) }
%Y A081170 Cf. A080825.
%K A081170 easy,nonn,tabf
%O A081170 3,1
%A A081170 _Cino Hilliard_, Apr 16 2003