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 (four 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:
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