In mathematics, a heptagonal pyramidal number is a figurate number representing the number of dots in a three-dimensional pattern in the shape of a heptagonal pyramid.
The first few heptagonal pyramidal numbers are:
1, 8, 26, 60, 115, 196, 308, 456, 645, 880, 1166, 1508, 1911, ... (sequence A002413 in the OEIS)The nth heptagonal number can be calculated by adding up the first n heptagonal numbers, or more directly by using the formula
References
Heptagonal pyramidal number Wikipedia(Text) CC BY-SA