Pyramidal numbers

(Math.)

certain series of figurate numbers expressing the number of balls or points that may be arranged in the form of pyramids. Thus 1, 4, 10, 20, 35, etc., are triangular pyramidal numbers; and 1, 5, 14, 30, 55, etc., are square pyramidal numbers.

pyramidal numbers

[¦pir·ə‚mid·əl ′nəm·bərz] (mathematics) The numbers 1, 4, 10, 20, 35, …, which are the number of dots in successive pyramidal arrays and are given by (1/6) n (n + 1) (n + 2), where n = 1, 2, 3, ….

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