xdenser

        function intArithm(){
        var
            max_a0 = +process.argv[2],
            longest = 0,
            max_len = 0, a0,len, a,z;

        for(a0=1;a0<=max_a0;++a0){
            a = a0;
            len = 0;
            while( a != 1){
                len++;
                z = a >>> 1;
                a = (!(a&1))?z:(a+z+1);
            }
            if(len>max_len){
                max_len = len;
                longest = a0;
            }
        }
        console.log(max_len,longest);
        }

   329 837799
   naive 3.06 sec
   329 837799
   decompozed 3.03 sec
   329 837799
   memoized decompozed 0.52 sec