## triangular numberAny number that can be represented by a triangular array of dots. 1, 3, 6, 10, ... are triangular numbers. The nth triangular number is n(n
+ 1)/2. Every integer is the sum of at most three triangular numbers. Every
even triangular number is a perfect number.
If T is a triangular number, 8T + 1 is a perfect square
and 9T + 1 is another triangular number. The square
of the nth triangular number is equal to the sum of the first n
cubes. Certain triangular numbers are also
squares, but no triangular number can be a third, fourth or fifth power,
nor can one end in 2, 4, 7, or 9. ## Related category• TYPES OF NUMBERS | |||||

Home • About • Copyright © The Worlds of David Darling • Encyclopedia of Alternative Energy • Contact |