Hexagonal pyramidal number

A hexagonal pyramidal number is a pyramidal number formed by adding the first n hexagonal numbers. The first few hexagonal pyramidal numbers are:

1, 7, 22, 50, 95, 161, 252, 372, 525, 715, 946, 1222, 1547, 1925 (sequence A002412 in the OEIS).

The nth number in this sequence, representing the sum of the first n hexagonal numbers, is given by the formula

${\displaystyle {\frac {n(n+1)(4n-1)}{6}}.}$

References

• Hexagonal pyramidal number at MathWorld