Copyright © University of Cambridge. All rights reserved.

'Forgotten Number' printed from http://nrich.maths.org/

Show menu


1 factorial = 1
2 factorial = 1 x 2 = 2
3 factorial = 1 x 2 x 3 = 6
4 factorial = 1 x 2 x 3 x 4 = 24
5 factorial = 1 x 2 x 3 x 4 x 5 = 120...

The triangle numbers are 1, 3, 6, 10, 15, 21...