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:
- Triangular pyramidal number (three sides)
- Square pyramidal number (4 sides)
- Pentagonal pyramidal number (five sides)
- Hexagonal pyramidal number (six sides)
- Heptagonal pyramidal number (seven sides)
the formula for a r-gonal pyramid number is:
![{\displaystyle X={\frac {3n^{2}+n^{3}[r-2]-n[r-5]}{6}}}](https://services.fandom.com/mathoid-facade/v1/media/math/render/svg/ce6ae9b50f82b0a52d2d8ea669a355c195983bee)
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ar:عدد هرمي
da:Pyramidetal
eo:Piramida nombro
pl:Liczby piramidalne