Analyse de boucles triangulaires

Déterminer la complexité $\Theta$ des fonctions suivantes :

def g1(n):
    s = 0
    for i in range(n):
        for j in range(i+1, n):
            s += i * j
    return s

def g2(n):
    s = 0
    for i in range(n):
        for j in range(n):
            for k in range(n):
                if i < j < k:
                    s += 1
    return s

def g3(n):
    s = 0
    for i in range(1, n+1):
        for j in range(1, i+1):
            for k in range(1, j+1):
                s += 1
    return s