go2 =>
   time(max_chain(MaxN,MaxLen)),
   printf("MaxN=%w,MaxLen=%w%n",MaxN,MaxLen).

table (-,max)
max_chain(N,Len) =>
    between(2,99_999,N),
    gen(N,Len).

table (+,-)
gen(1,Len) => Len=1.
gen(N,Len), N mod 2 == 0 =>
    gen(N div 2,Len1),
    Len=Len1+1.
gen(N,Len) =>
    gen(3*N+1,Len1),
    Len=Len1+1.