Triangular Numbers Using Loops (Python)

Question

I'm currently working on a project that I'm working on, and I'm currently learning about looping. Here is the direction as follows...

Triangular numbers are numbers of objects that could be arranged in a triangle by making rows, with one more object in each row than in the previous row. Write a function that given a number, n, will formulaically compute the nth Triangular number. Write another function that displays the Triangular numbers up to and including n.

The formula states (n(n+1))/(2) or (n^(2)+n)/(2)

So pretty much I think I would need to formulate a function that whatever I enter for n to the equation I would get the answer. However, my question is I don't understand how loops is used in this scenario. I have done the following but I'm getting an error. I think it should very simple right?

n=int(input("Please Enter n:"))
y1=((n**2)+n)/(2)   
print (y1)

I think the code above answers the first question where it formulaically compute the nth Triangular number, given inputing n. However, I'm having a hard time to write a function for the second question where a function that displays the Triangular numbers up to and including n. Thank you very much for your help.

Peter Pei Guo · Accepted Answer · 2014-09-26 01:20:57Z

2

Could be something like this:

def all_triangle_numbers(n):
    for i in range(1, n + 1):   
        print("n = {0}, triangle = {1}".format(i, (i ** 2 + i)//2))

all_triangle_numbers(10)

edited Sep 26, 2014 at 1:20

answered Sep 26, 2014 at 1:14

Peter Pei Guo

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4 Comments

python2learn Over a year ago

Thanks you. Would you be able to help me for the second question? I'm having a hard time to write a function for the second question where a function that displays the Triangular numbers up to and including n.(Which I don't get quite what it means in the first place).

python2learn Over a year ago

Thank you for your work. But, I'm having trouble because it asks up to and including n. How does that work?

python2learn Over a year ago

I'm using an online complier, but it does work. I see from 1 to 10.

Peter Pei Guo Over a year ago

Glad I helped, enjoy!

A.J. Uppal · Accepted Answer · 2014-09-26 01:56:19Z

0

You are probably getting an error because of your input(), which should be raw_input(). However, if that is not the case, please state exactly what error you are getting.

Here is some working code:

def triangle(n):
    return ((n**2)+2)/2.0

n = int(raw_input('Please enter an integer: '))
print triangle(n)

Or, to print all the triangle numbers up to and including n:

def all_triangles(n):
    for i in range(1, n+1):
        print ((i**2)+2)/2.0,

n = int(raw_input('Please enter an integer: '))
all_triangles(n)

edited Sep 26, 2014 at 1:56

answered Sep 26, 2014 at 1:12

A.J. Uppal

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3 Comments

python2learn Over a year ago

I think the code actually works, but I will try out yours as well. Would you be able to help me for the second question? I'm having a hard time to write a function for the second question where a function that displays the Triangular numbers up to and including n.(Which I don't get quite what it means in the first place).

T.Woody Over a year ago

@python2learn, it sounds like this is the original first question that you had. This is the part that it is asking for either a for loop or a while loop. If this were me, I would make a while loop that states: while (n>=0){#stuff; --n}. Maybe this can implemented into the above answer?

python2learn Over a year ago

Sorry I'm having trouble grasping on it. Would you be able to show me?

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