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Heptagonal Number

\begin{figure}\begin{center}\BoxedEPSF{HeptagonalNumber.epsf scaled 600}\end{center}\end{figure}

A Figurate Number of the form $n(5n-3)/2$. The first few are 1, 7, 18, 34, 55, 81, 112, ... (Sloane's A000566). The Generating Function for the heptagonal numbers is



Sloane, N. J. A. Sequence A000566/M4358 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