Hexagonal Pyramidal Number

A Pyramidal Number of the form $n(n+1)(4n-1)/6$, The first few are 1, 7, 22, 50, 95, ... (Sloane's A002412). The Generating Function of the hexagonal pyramidal numbers is

$${x(3x+1)\over(x-1)^4}=x+7x^2+22x^3+50x^4+\ldots.$$

References

Sloane, N. J. A. Sequence A002412/M4374 in ``An On-Line Version of the Encyclopedia of Integer Sequences.'' http://www.research.att.com/~njas/sequences/eisonline.html and Sloane, N. J. A. and Plouffe, S. The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.