collatz-graph.gv

digraph {

node[style=filled,color=".7 .3 1.0"];

1

node[style=filled,color=".95 .1 1"];
2 -> 1;
3 -> 10 -> 5 -> 16 -> 8 -> 4 -> 2;
4;
5;
6 -> 3;
7 -> 22 -> 11 -> 34 -> 17 -> 52 -> 26 -> 13 -> 40 -> 20 -> 10;
8;
9 -> 28 -> 14 -> 7;
10;
11;
12 -> 6;
13;
14;
}