Other
Fascinating Triangular Numbers
Patterns of numbers don't come along every day, and so when they do, they need to be bragged about! The basic definition of triangular numbers begins this site which also lists many of the properties of these numbers, highlights the...
Illustrative Mathematics
Illustrative Mathematics: F Le Triangular Numbers
The goal of this task is to work on producing a quadratic equation from the arithmetic context of triangular numbers. Aligns with HSF-LE.A.
Cut the Knot
Cut the Knot!: What Is a Number?
Casual and clear but definitely upper-level discussion of rational, real, imaginary, and several other types of numbers. Links to related sites.
National Council of Teachers of Mathematics
The Math Forum: Pascal's Triangle
You will find the triangular numbers in Pascal's triangle.
Curated OER
Displaying Triangular Numbers
Patterns of numbers don't come along every day, and so when they do, they need to be bragged about! The basic definition of triangular numbers begins this site which also lists many of the properties of these numbers, highlights the...
Texas Instruments
Texas Instruments: Bats Triangular
In this activity, students use manipulatives to construct a pyramid. The manipulative pyramid then becomes the basis students use to construct a pictorial representation of a pyramid. The TI-10 is used to show symbolic representation of...
Texas Instruments
Texas Instruments: Numb3 Rs: Dial the Phone
Based off of the hit television show NUMB3RS, this lesson gives students some insight into the connection between graph theory and triangular numbers, using telephone networks. Similar to the famous Handshake Problem, students will find...
Wolfram Research
Wolfram Science World: Pythagoras of Samos (Ca. 560 Ca. 480 Bc)
This site from ScienceWorld provides a short, informative description of many of the contributions of Pythagoras to mathematics. Links exist to some of the contributions as well as to additional information.
Math Is Fun
Math Is Fun: Common Number Patterns
Developed by a mathematics teacher from the UK, this page identifies and illustrates several common number patterns.