Let f be a function on rationals p/q (p,q coprime) defined by f(p/q) = abs(p-q)/nextoddColl(p) (so the denominator is the next odd number in the Collatz trajectory of p). Start with f(n/1) and repeat application of f until it reaches again an integer, which is a(n). If no integer is reached, then a(n)=0.