Heptagonal Pyramidal Number
A Pyramidal Number of the form 
, The first few are 1, 8, 26, 60, 115, ... (Sloane's A002413). TheGenerating Function for the heptagonal pyramidal numbers is
References
Sloane, N. J. A. SequenceA002413/M4498in ``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.
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