collatz.py

mex=1
while(True):
    print(mex)
    X=mex
    S={X}
    while(X>1):
        if X%2==0:
            X//=2
        else:
            X=3*X+1
        if X<mex:
            break
        elif X in S:
            print("hanrei",X)
            assert False
        else:
            S.add(X)
    mex+=1