def is_triangular(num):
    b = 1
    summ = 1
    while summ < num:
        b = b + 1
        summ = summ + b
    if summ == num:
        return b
    else:
        return 0

"""
Using the previous function
"""
def triangulars (maxn):
    lt = []
    for i in range(1, maxn+1):
        b = is_triangular(i)
        if b!=0:
            lt.append((i, b))
    return lt

"""
Direct version
"""
def triangulars_2(maxn):
    i = 1
    t = 1
    lt =[] 
    while t <=maxn:
        lt.append((t, i))
        i = i + 1
        t = t + i
    return lt

# your choice
#triangulars = triangulars_1
triangulars = triangulars_2