A pyramidal number is a figurate number that represents a pyramid with a base and a given number of sides. The term is most often used to refer to square pyramidal numbers, which have four sides, but it can also refer to:

the formula for a r-gonal pyramid number is:

$ X= \frac{3n^2+n^3[r-2]-n[r-5]}{6} $

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ar:عدد هرمي

da:Pyramidetaleo:Piramida nombro pl:Liczby piramidalne

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