Number: Tetrahedral Number

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Index Entry

Number: Tetrahedral Number:

"N² - N is always a triangular number as, for instance, the

number of balls in the rack on a pool table. A telephone

connection is a circuit; a circuit is a circle; two people

need one circuit and three people need three circles, which

make a triangle. Four people need six circuits, and six

circuits cluster most economically and symmetrically in a

triangle. Five people need 10 private circuits, six people

need 15, and seven people need 21, and so on: all are

triangular numbers.

"Successive stackings of the number of relationships of our

experiences are a stacking of triangles. The number of balls

in the longest row of any triangular cluster will always be

the same number as the number of rows of balls in the

triangle, each row always having one more than the preceding

row. The number of balls in any triangle will always be

(R + 1)² - (R + 1) where R = the number of rows

2

(or the number of balls in the longest row)."