theorem :: FIB_NUM2:70

for n being non zero Element of NAT holds {((Fib n) * (Fib (n + 3))),((2 * (Fib (n + 1))) * (Fib (n + 2))),(((Fib (n + 1)) ^2) + ((Fib (n + 2)) ^2))} is Pythagorean_triple