Features in the General Predecessor Tree

-- we adopt the computer science convention that trees' roots are at the top
-- whence a Collatz iteration goes upward on a page and predecessors appear below their Collatz successors
-- "extensions" in a level all give a common successor
-- extensions go as 4n+1 and are in {5[8]}
-- "leaf nodes" in {0[3]}              
-- we use "one-step" formulae, omitting all even integers, to calculate
     -- the successor of n, T_s(n)=(3*n+1)/2ⁱ               eqn 1
                                 where i produces an odd T_s
     -- the predecessor of n, T_p(n)=(-1+n*2ⁱ)/3          eqn 2
                                 where i must be even when n in {1[3]}
                                     and i must be odd when n in {2[3]}.