1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

Mathematically, we write it as:

F(n) = F(n) + F(n-1)

This can easily be done in Python, using generators.

def Fibonacci(n):

a, b = 1, 1

while b < n:

yield b

a, b = b, a + b

To print all the Fibonacci numbers less than 4000000,a, b = 1, 1

while b < n:

yield b

a, b = b, a + b

for i in Fibonacci(4000000):

print i,

Output:print i,

>>> 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765 10946 17711 28657 46368 75025 121393 196418 317811 514229 832040 1346269 2178309 3524578