factr(0,1).
factr(N,F):- J is N-1,factr(J,F1), F is N*F1.

facti(N,F):-facti(0,1,N,F).
facti(N,F,N,F).
facti(I,Fi,N,F):- J is I+1, Fj is J*Fi, facti(J,Fj,N,F).

fib(0,1).
fib(1,1).
fib(N,F):-N1 is N-1, N2 is N-2,fib(N1,F1), fib(N2,F2), F is F1+F2.

fibt(0,1).
fibt(1,1).
fibt(N,F):-fibt(2,1,1,N,F).
fibt(N,Last2,Last1,N,F):-F is Last1+Last2.
fibt(I,Last2,Last1,N,F):-
	J is I+1,
	Fi is Last1+Last2,
	fibt(J,Last1,Fi,N,F).