Programme ecrit_2008_rattrapage_43_.py

# coding: latin-1
def u_non_recursif (n) :
    if n <= 2 : return 1
    u0 = 1
    u1 = 1
    u2 = 1
    i = 3
    while i <= n :
        u  = u0 + u1 + u2
        u0 = u1
        u1 = u2
        u2 = u
        i += 1
    return u