Welcome to Computing Corner (renamed in light of new English National Curriculum) this is a regular column about computing and coding in the classroom. Written by Dan Aldred (@Dan_Aldred) who is well worth a follow on Twitter. Dan’s article is about his students use of programming to work with triangular numbers.

Charles Babbage or ‘Cabbage’ (as many of my students refer to him), spent a considerable amount of his time calculating all sorts of numerical values. This included triangular numbers. He was fascinated with statistics and used information and data to make predictions, calculations and decisions surrounding what might happen. Babbage was so obsessed with this, that he created an engine that would allow him to input a number; the machine would process it and then produce an output. He called it the ‘Difference Engine’. This was the beginning of computation even though the machine was only a theoretical model with smaller working example models. A complete working version was never built, but Babbage’s thinking was way ahead of his time.

Babbage spent numerous pain staking years calculating and recording these numbers in books and selling them to engineers, accountants and scientists. What is incredible is that 200 years later, in the present day we can code a simple program that will calculate any number of triangular numbers that you so desire.

I asked my students to think about triangular numbers and how they could work them out, we come up various formulas,

For example to calculate the 10thtriangular number, (where zero is the first triangular number)

((The position of the triangular number minus 1)multiplied by 0.5)) multiplied by the position of the triangular number


Next step was to create a program to test the formulas, using Python,

This was a great exercise to introduce and use the ‘definition’ feature. A definition allows you to create a set of steps or procedures that are called by a single name, for example the formula to calculate the triangular number,


"Print the Triangular numbers for a given list"

tn1 = (n-1)*0.5

tnf = tn1*n


Then the user can call the definition by using the name of it, triangle_ value(insert a number of your choice). It saves time having to type out the formula for every single number that you enter.

The program can then be adapted to add in a pause and use a while statement to count down the triangular numbers from say, 10 to 0.

import time


"Print the Triangular numbers for a given list"

while n > 0:

tn1 = (n-1)*0.5

tnf = tn1*n

print "The", n, "Triangular number is", tnf

n = n – 1


x = input("Enter how many triangular numbers you want to find?")


I hope this has inspired you to try some of this programming at home.

Dan’s new website has some brilliant ‘How to’ programming guides


Dan Aldred is a teacher of Computing and Head of IT. He is also a member of the school extended leadership team and teacher learning group.  He’s interested in how technology and software move learning forward.

Written by Julian S Wood -"rel="author"
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