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Pentagonal Pyramidal Number

A Pyramidal Number of the form $n^2(n+1)/2$. The first few are 1, 6, 18, 40, 75, ... (Sloane's A002411). The Generating Function for the pentagonal pyramidal numbers is



Sloane, N. J. A. Sequence A002411/M4116 in ``An On-Line Version of the Encyclopedia of Integer Sequences.'' and Sloane, N. J. A. and Plouffe, S. The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.

© 1996-9 Eric W. Weisstein