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 A081171 #4 Oct 01 2013 17:57:36
%S A081171 1,0,2,1,3,0,4,2,1,5,2,1,6,3,7,4,2,1,8,4,2,1,9,6,3,10,5,11,8,4,2,1,12,
%T A081171 6,3,13,10,5,14,7,4,2,1,15,12,6,3,16,8,4,2,1,17,14,7,4,2,1,18,9,6,3,
%U A081171 19,16,8,4,2,1,20,10,5,21,18,9,6,3,22,11,8,4,2,1,23,20,10,5,24,12,6,3,25,22
%N A081171 Triangle in which n-th row gives trajectory of n (including n itself) under the map x -> x/2 if x is even, x -> 3x-3 if x is odd, stopping when reaching one of 1, 3, 5, 15, 51.
%o A081171 (PARI) xn1m3(n) = { for(x=1,n, x1=x; print1(x1" "); while(x1>1, if(x1%2==0,x1/=2,x1=3*x1-3); print1(x1" "); ) ) }
%Y A081171 Cf. A080825.
%K A081171 easy,nonn,tabf
%O A081171 1,3
%A A081171 _Cino Hilliard_, Apr 16 2003